Markus, this is a huge step backwards.
I maintain multiple AMO collections that have followers. Sometimes I need to add a new extension to up to 5 different collections (sometimes even more).
This was simple and fluid with the previous design.
Now, I have to go to each collection, manually type in the name of the new extension, search for it, and then add it. I then have to repeat that process for each collection.
If I have to do this for 5 extensions, it could mean over 1000 keypresses and button-clicks compared to what previously took about 20 clicks.
In other words, the new process is too onerous to even consider using. The bottom line is that I will no longer be maintaining any of my AMO collections. I doubt other collection curators will go through the now laborious and tedious process either.
I also actively added interesting extensions to my personal favorites. The new design makes that process tedious at best. I think I’ll just go back to creating an offline text file; it’s much easier. Unfortunately, with that workaround, no one else in the community benefits.
If Mozilla needs help with usability issues like these, let me know. I happen to be a human factors engineer (UI/UX professional).
I project that the result of the new design will be less interest in AMO as a community. The AMO community is one of the primary attractions to Firefox over the competition. This new design is not in the best interest of Mozilla.