I was thinking a new feature that can be used in this addon:
Instead of going into the addon menu on the pause menu to disable a Ambient/Combat Music pack: why not create an options menu in game that can enable and disable music packs.
For example:

Nombat Options
Chose Music Pack:
[x] Metal Gear Solid 3
[x] Undertale
[x] Half Life 2

Lets just say that I want to have one music pack that has a sneeky beeky theme on a map I am playing; I can enable or disable any of the music packs that can fit to my needs. Since Metal Gear Solid 3 is an option i can disable some of the music packs that i don't want to hear:

Nombat Options
Chose Music Pack:
[x] Metal Gear Solid 3
[ ] Undertale
[ ] Half Life 2

That way i don't need to painstakingly manuver on the dreadful gmods addons menu to disable a music pack.

Thanks for reading, and i hope you can take this idea into consideration.

P.S. As a side note, for servers people can chose which music that they want to hear if the admin of the server can allow it. I can't speak much on servers but that is also an idea that i can say for this option.