Implemented a filter for the theme preferences based on the proposel "https://blender.community/c/rightclickselect/kSdbbc/".
This can drastically improve theme creation ease.
It can operate on either the properties or a selected color.
The first compares labels and descriptions as well as their translation.
The latter can be used to find the same or similar colors, based on the precision. To not filter out the currently edited color by the user, a freeze-results button is also added.
I saw there is also a general task for searching/filtering within the properties: "https://developer.blender.org/T71185".
So in the future, this theme filtering patch might get obsolete.
In the current implementation, there is a lot of the filtering hard coded.
I would highly appreciate a hint to make the system more automatic.