An addition of 2 features brought up by users.
Rahi Delvi suggested an option to display the search bar at the top. I like his reasoning of line of sight and the changing height of the popup while searching. And he uses SimpleExtManager like a pro! Option added!
Александр Мелихов has done extensive grouping with his extensions and found that the "add to group" context menu doesn't scroll. This is one point that has eluded from testing. The menu now scrolls.
Strange me. The search is there but I just like scrolling and visually finding that extension. I don't really group extensions too, I have only 3 groups which I hardly interact with :P