Currently scripts can only be used in virtual fields.
It would be nice if scripts could be used as functions to be associated with buttons.
You could edit tags without using virtuals.
Virtual Tags are only used for specifying what is displayed on-screen, so I'm not sure how that would work for editing values.
To address your numbered examples:
1) change the color of a text based on a comparison.
This seems out of place, as it is unrelated to tagging or buttons.
However, MusicBee supports these custom
Markup functions in Virtual Tags:

2) delete text again based on a comparison.
3) add text to a tag
4) copy part of a tag to one that already exists
Based on these other suggestions and your apparent willingness to learn simple scripting commands, it sounds like you should add Mp3tag to your workflow:
https://www.mp3tag.de/en/index.htmlUsing the language already in MB but associated with a button that then generates a loop between all the tracks seems much easier to me than having to learn a language from scratch.
By the way, MB's language is so simple that with a little practice you can really do a lot of routines.
You will have to learn Mp3tag's own built-in scripting commands, but they're well-documented and not unlike MusicBee's virtual tag functions so it isn't too hard.
https://docs.mp3tag.de/scriptinge.g.
$Left(%TagName%, 3)
$If($Eql(%Artist%,The Beatles),English,Not English))
You can combine any number of separate commands to build up a library of custom tagging Actions to tag your files quickly and consistently.
Bee excellent to each other...