diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9e1258a52..94579c16e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,7 @@
 ### Detailed list of changes
 
 * Added alternative emulators support where additional emulators can be defined in es_systems.xml and be selected system-wide or per game via the user interface
+* Added the ability to make complementary game system customizations without having to replace the entire bundled es_systems.xml file
 * Added a menu option to change the application exit key combination
 * Expanded the themeable options for "helpsystem" to support custom button graphics, dimmed text and icon colors, upper/lower/camel case and custom spacing
 * Removed the "Choose" entry from the help prompts in the gamelist view
diff --git a/INSTALL-DEV.md b/INSTALL-DEV.md
index 273b4e4c3..cad4304cd 100644
--- a/INSTALL-DEV.md
+++ b/INSTALL-DEV.md
@@ -1399,16 +1399,16 @@ For the following options, the es_settings.xml file is immediately updated/saved
 
 ## es_systems.xml
 
-The es_systems.xml file contains the system configuration data for ES-DE, written in XML format. This defines the system name, the full system name, the ROM path, the allowed file extensions, the launch command, the platform (for scraping) and the theme to use.
+The es_systems.xml file contains the game systems configuration data for ES-DE, written in XML format. This defines the system name, the full system name, the ROM path, the allowed file extensions, the launch command, the platform (for scraping) and the theme to use.
 
-ES-DE ships with a comprehensive `es_systems.xml` configuration file and normally you shouldn't need to modify this. However there may be special circumstances such as wanting to use alternative emulators for some game systems or perhaps you need to add additional systems altogether.
+ES-DE ships with a comprehensive `es_systems.xml` file and most users will probably never need to make any customizations. But there may be special circumstances such as wanting to use different emulators for some game systems or perhaps wanting to add additional systems altogether.
 
-To make a customized version of the systems configuration file, it first needs to be copied to `~/.emulationstation/custom_systems/es_systems.xml`. (The tilde symbol `~` translates to `$HOME` on Unix and macOS, and to `%HOMEPATH%` on Windows unless overridden using the --home command line option.)
+To accomplish this, ES-DE supports customizations via a separate es_systems.xml file that is to be placed in the `custom_systems` folder in the application home directory, i.e. `~/.emulationstation/custom_systems/es_systems.xml`. (The tilde symbol `~` translates to `$HOME` on Unix and macOS, and to `%HOMEPATH%` on Windows unless overridden via the --home command line option.)
+
+This custom file functionality is designed to be complementary to the bundled es_systems.xml file, meaning you should only add entries to the custom configuration file for game systems that you actually want to add or override. So for the example of customizing a single system, this file should only contain a single `<system>` tag. The structure of the custom file is identical to the bundled file with the exception of an additional optional tag named `<loadExclusive/>`. If this is placed in the custom es_systems.xml file, ES-DE will not load the bundled file. This is normally not recommended and should only be used for special situations. At the end of this section you can find an example of a custom es_systems.xml file.
 
 The bundled es_systems.xml file is located in the resources directory that is part of the application installation. For example this could be `/usr/share/emulationstation/resources/systems/unix/es_systems.xml` on Unix, `/Applications/EmulationStation Desktop Edition.app/Contents/Resources/resources/systems/macos/es_systems.xml` on macOS or `C:\Program Files\EmulationStation-DE\resources\systems\windows\es_systems.xml` on Windows. The actual location may differ from these examples of course, depending on where ES-DE has been installed.
 
-Note that when copying the bundled es_systems.xml file to ~/.emulationstation/custom_systems/, it will completely replace the default file processing. So when upgrading to future ES-DE versions, any modifications such as additional game systems will not be enabled until the customized configuration file has been manually updated.
-
 It doesn't matter in which order you define the systems as they will be sorted by the full system name inside the application, but it's still probably a good idea to add them in alphabetical order to make the file easier to maintain.
 
 Keep in mind that you have to set up your emulators separately from ES-DE as the es_systems.xml file assumes that your emulator environment is properly configured.
@@ -1424,7 +1424,7 @@ Below is an overview of the file layout with various examples. For the command t
     <system>
         <!-- A short name. Although there can be multiple identical <name> tags in the file, upon successful loading of a system,
         any succeeding entries with identical <name> tags will be skipped. Multiple identical name tags is only required for very
-        special situations so it's normally recommended to keep this tag unique.-->
+        special situations so it's normally recommended to keep this tag unique. -->
         <name>snes</name>
 
         <!-- The full system name, used for sorting the systems, for selecting the systems to multi-scrape etc. -->
@@ -1567,6 +1567,42 @@ And finally one for Windows:
 </system>
 ```
 
+As well, here's an example on Unix of a custom es_systems.xml file placed in ~/.emulationstation/custom_systems/ that overrides a single game system from the bundled configuration file:
+```xml
+<?xml version="1.0"?>
+<!-- This is a custom ES-DE game systems configuration file for Unix -->
+<systemList>
+    <system>
+        <name>nes</name>
+        <fullname>Nintendo Entertainment System</fullname>
+        <path>%ROMPATH%/nes</path>
+        <extension>.nes .NES .zip .ZIP</extension>
+        <command>/usr/games/fceux %ROM%</command>
+        <platform>nes</platform>
+        <theme>nes</theme>
+    </system>
+</systemList>
+```
+
+If adding the `<loadExclusive/>` tag to the file, the bundled es_systems.xml file will not be processed. For this example it wouldn't be a very good idea as NES would then be the only platform that could be used in ES-DE.
+
+```xml
+<?xml version="1.0"?>
+<!-- This is a custom ES-DE game systems configuration file for Unix -->
+<loadExclusive/>
+<systemList>
+    <system>
+        <name>nes</name>
+        <fullname>Nintendo Entertainment System</fullname>
+        <path>%ROMPATH%/nes</path>
+        <extension>.nes .NES .zip .ZIP</extension>
+        <command>/usr/games/fceux %ROM%</command>
+        <platform>nes</platform>
+        <theme>nes</theme>
+    </system>
+</systemList>
+```
+
 ## es_find_rules.xml
 
 This file makes it possible to define rules for where to search for the emulator binaries and emulator cores.
diff --git a/THEMES-DEV.md b/THEMES-DEV.md
index 8999bee1b..a42c00152 100644
--- a/THEMES-DEV.md
+++ b/THEMES-DEV.md
@@ -864,9 +864,9 @@ EmulationStation borrows the concept of "nine patches" from Android (or "9-Slice
     - Where on the component `pos` refers to. For example, an origin of `0.5 0.5` and a `pos` of `0.5 0.5` would place
       the component exactly in the middle of the screen.
 * `textColor` - type: COLOR. Default is 777777FF.
-* `textColorDimmed` - type: COLOR. Default is the same value as textColor.
+* `textColorDimmed` - type: COLOR. Default is the same value as textColor. Must be placed under the 'system' view.
 * `iconColor` - type: COLOR. Default is 777777FF.
-* `iconColorDimmed` - type: COLOR. Default is the same value as iconColor.
+* `iconColorDimmed` - type: COLOR. Default is the same value as iconColor. Must be placed under the 'system' view.
 * `fontPath` - type: PATH.
 * `fontSize` - type: FLOAT.
 * `entrySpacing` - type: FLOAT. Default is 16.0.
diff --git a/USERGUIDE-DEV.md b/USERGUIDE-DEV.md
index dcbb2d736..83dd4cae3 100644
--- a/USERGUIDE-DEV.md
+++ b/USERGUIDE-DEV.md
@@ -77,9 +77,9 @@ On Unix this means /home/\<username\>/.emulationstation/, on macOS /Users/\<user
 
 **Note:** As of ES-DE v1.1 there is no internationalization support, which means that the application will always require the physical rather than the localized path to your home directory. For instance on macOS configured for the Swedish language /Users/myusername will be the physical path but /Användare/myusername is the localized path that is actually shown in the user interface. The same is true on Windows where the directories would be C:\Users\myusername and C:\Användare\myusername respectively. If attempting to enter the localized path for any directory-related setting, ES-DE will not be able to find it. But it's always possible to use the tilde `~` symbol when referring to your home directory, which ES-DE will expand to the physical location regardless of what language you have configured for your operating system. If you're using an English-localized system, this whole point is irrelevant as the physical and localized paths are then identical.
 
-It's also possible to override the home directory path using the --home command line option, but this is normally required only for very special situations so we can safely ignore that option for now.
+It's possible to override the home directory path using the --home command line option, but this is normally required only for very special situations so we can safely ignore that option for now.
 
-Also on first startup the configuration file `es_settings.xml` will be generated in the ES-DE home directory, containing all the application settings at their default values. Following this, a file named `es_systems.xml` will be loaded from the resources directory (which is part of the ES-DE installation). This file contains the game system definitions including which emulator to use per platform. For some systems there are also alternative emulators defined which can be applied system-wide or per game. How that works is explained later in this guide. The systems configuration file can also be customized, as described in the next section.
+Also on first startup the configuration file `es_settings.xml` will be generated in the ES-DE home directory, containing all the application settings at their default values. Following this, a file named `es_systems.xml` will be loaded from the resources directory (which is part of the ES-DE installation). This file contains the game system definitions including which emulator to use per platform. For some systems there are also alternative emulators defined which can be applied system-wide or per game. How that works is explained later in this guide. A customized systems configuration file can also be used, as described in the next section.
 
 There's an application log file created in the ES-DE home directory named `es_log.txt`, please refer to this in case of any issues as it should hopefully provide information on what went wrong. Starting ES-DE with the --debug flag provides even more detailed information.
 
@@ -118,6 +118,8 @@ genesis: Sega Genesis
 gx4000: Amstrad GX4000
 ```
 
+If a custom es_systems.xml file is present in ~/.emulationstation/custom_systems/ any entries from this file will have their names trailed by the text _(custom system)_. So if the GameCube system in the example above would be present in the custom systems configuration file, the system would be shown as `gc (custom system)` instead of simply `gc`. This is only applicable for the systems.txt and systeminfo.txt files, the trailing text is not applied or used anywhere else in the application.
+
 Note that neither the systeminfo.txt files or the systems.txt file are needed to run ES-DE, they're only generated as a convenience to help with the setup.
 
 There will be a lot of directories created if using the es_systems.xml file bundled with the installation, so it may be a good idea to remove the ones you don't need. It's recommended to move them to another location to be able to use them later if more systems should be added. For example a directory named _DISABLED could be created inside the ROMs folder (i.e. ~/ROMs/_DISABLED) and all game system directories you don't need could be moved there. Doing this reduces the application startup time as ES-DE would otherwise need to scan for game files for all these systems.
@@ -126,9 +128,15 @@ There will be a lot of directories created if using the es_systems.xml file bund
 _This is the dialog shown if no game files were found. It lets you configure the ROM directory if you don't want to use the default one, and you can also generate the game systems directory structure. Note that the directory is the physical path, and that your operating system may present this as a localized path if you are using a language other than English._
 
 
-## Customizing the systems configuration file
+## Game system customizations
 
-The `es_systems.xml` file is located in the ES-DE resources directory which is part of the application installation. As such this file is not intended to be modified directly. If a customized file is needed, this should instead be placed in the `custom_systems` folder in the ES-DE home directory, i.e. `~/.emulationstation/custom_systems/es_systems.xml`. You can find information on the file structure and how to adapt the configuration in the [INSTALL-DEV.md](INSTALL-DEV.md#es_systemsxml) document.
+The game systems configuration file `es_systems.xml` is located in the ES-DE resources directory which is part of the application installation. As such this file is not intended to be modified directly. If system customizations are required, a separate es_systems.xml file should instead be placed in the `custom_systems` folder in the ES-DE home directory, i.e. `~/.emulationstation/custom_systems/es_systems.xml`.
+
+Although it's possible to make a copy of the bundled configuration file, modify it and then place it in this directory, that is not how the custom file is designed to be used. Instead the intention is that the file placed in the custom_systems directory complements the bundled file, meaning only the systems that are to be  customized or added should be included. For example you may want to replace the emulator, modify the full name or change the supported file extensions for a single system. In this case it wouldn't make sense to add the complete bundled file with these minor modifications. Also, future updates to ES-DE may contain changes to existing emulator entries which would then not be used as the custom file takes precedence over the bundled file.
+
+To clarify, the custom es_systems.xml file is loaded first, followed by the bundled file.
+
+Although unlikely to be needed, it's also possible to skip the loading of the bundled es_systems.xml file and only use the file in custom_systems. The instructions for how to accomplish this as well as how to adapt the es_systems.xml file can be found in [INSTALL-DEV.md](INSTALL-DEV.md#es_systemsxml).
 
 
 ## Migrating from other EmulationStation forks