ES-DE/themes/linear-es-de/custom-collections/theme.xml

<theme>
    <include>./../theme.xml</include>

    <variant name="all">
        <view name="gamelist">
            <text name="systemName">
                <text>${langCustomCollections}</text>
                <letterCase>capitalize</letterCase>
            </text>
            <text name="system-label">
                <metadata>systemFullname</metadata>
                <defaultValue>${langYourCollections}</defaultValue>
            </text>
        </view>
    </variant>

    <variant name="simpleTextlistWithVideos, simpleTextlistWithoutVideos,
                   carousel, simpleCarousel">
        <view name="gamelist">
            <text name="customCollectionName">
                <metadata>systemFullname</metadata>
                <defaultValue>${langYourCollections}</defaultValue>
            </text>
        </view>
    </variant>
</theme>