When you have a lot of themes and a lot of theme components it can be hard to ensure that your components are turned on for all the themes you want them to be on for (and only those).
The idea of the Theme Component Matrix is that it would show you at a glance all of your themes and their components. In the mockup I made it just says Yes/No, but those would be links letting you instantly toggle the components.
If there are too many columns, maybe the component names could be rotated with CSS?
@Dannii This is an excellent idea!
Prior to doing anything in core maybe try 2 things:
A data explorer query for this
A theme component that adds Matrix 
I worry about adding complexity here to core.
Also on core’s side, I think it makes sense to show a list of “themes” that have a component in the actual customize menu for the component. Just need to be careful not to clutter that UI too much.
Bin gerade auf dieses Thema gestoßen, als ich nach einer solchen Daten-Explorer-Abfrage gesucht habe! Hat das schon jemand erstellt?
Die Benutzeroberfläche zur Verwaltung von Themes und Komponenten wurde seit Beginn dieses Themas dramatisch verbessert. Die Komponentenliste zeigt alle Themes an, auf denen jede Komponente verwendet wird:
