Glad to have Custom Scollbars be part of the Recommended Extensions program. I’ve actually been working on porting it to other browsers as well, so what @sylvaing said about uploading to Edge was helpful information.
As far as having developers explain why they need the permissions they ask for, I actually really like that idea. I do that in my AMO descriptions by linking to a wiki page on the add-on’s GitHub repo, but it would be really cool if it was actually a feature on AMO.
I used to do a lot of volunteering on SUMO (not so much at the moment due to other commitments) and there were often questions about why add-ons need permissions for certain things, especially when it comes to the blanket “Access your data for all websites” permission that scares a lot of users. It would be cool if developers had the option to add a brief explanation about why they need that permission so that users could see that on the AMO listing.
It would offer some transparency to users, especially since some permissions are worded really harsh. For example, Custom Scrollbars needs the “Access your data for all websites” permission to be able to change the scrollbar on websites, but the way that the permission is worded it sounds like the add-on is trying to mine your data and passwords (which is DEFINITELY not the case).