Before 5.8 it was possible to customize the components of a workspace theme, now it's no longer possible. Another problem: why is it possible for a workspace theme to change icons, but it's not possible to customize those icons from the Icons kcm? Reproducible: Always
See plasmathemeexplorer in plasma-sdk for editing and creating themes. >Another problem: why is it possible for a workspace theme to change icons, but it's not possible to customize those icons from the Icons kcm? Because they're part of the theme