Is there a way to remove IMPORTED and CUSTOM STYLES from SAB Styles Tab?
Without editing the .appdef file all you can do is to remove all styles so the selecors do nothing.
If you know what you are doing it is easy to remove these styles inside of the appdef file, of course after you close SAB.
Honestly, I do not understand the 1st sentence. What is “selecors”
How ‘to remove all styles’ when there is no way to do it only in the .appdef file …?
It seems to me that SAB would be easier to deal with (at times) for non-programmers if the appdef files could be cleaned up from the menus instead of manually by opening them in a text editor. But I do not know if this is relevant for many SAB users …?
It’s relevant for at least one other SAB user 
. I asked this question a few weeks ago. How to delete a custom style
I did poke around the appdef file and managed to delete the custom styles without messing anything else up, but I agree it would be nice to be able to delete from within SAB, although I don’t expect it would be needed very often. Probably a low-priority feature request.