Inside the "Scripts and Add-Ins" dialog you have the option to "Remove" a given add-in or script. This will not delete the add-in, but will simply mark it to be ignored in the future, and so it won't be listed or loaded anymore:
But how can you bring it back if you changed your mind? 🤔
1) Close Fusion 360 (if it's running)
2) Move the folder of the add-in to a temporary location - maybe place it in the trash?
3) Start Fusion 360 - it will realize that the add-in does not exist anymore, so it can delete the note about ignoring it
4) Close Fusion 360
5) Move the add-in's folder back where it was before
6) Start Fusion 360 - the add-in will show up in the list again 😀