Currently extensions are arranged/lit up by whether they have or need permissions to the current site. I had assumed the greyed out extensions were add-ons that were disabled.
Maybe the Unified Extensions feature could replicate the most useful features of the Add-ons Manager functionality (which is a separate, clunky tab).
1. List ALL add-ons, including disabled ones (just like Add-ons Manager, except in alphabetical order. This is because you can't Ctrl+F to Find an extension in Add-on Manager).
2. Each extension could have a enable/disable toggle. This would make it easy for testing/tinkering, and make it clear and accessible.
3. Change or remove the lengthy/confusing "can always read and change data on this site" etc. Maybe it could be an icon instead? I personally don't find it that useful.