The problem is that I just spent about an hour searching for a plugin (build timeout in my case) in the available plugins section, in the end going down to manually scanning the list believing that it may be displayed under a different name perhaps.

Well, turns out that the plugin was already installed, which hides it from the available list.

This should not be. I'm perfectly happy to have it marked differently, so I can see right away that it is installed - but it should at least be findable in that list. Because that plugin is most definitely available. It's also already installed, but it's definitely available. I'm also ok with a hide installed checkbox if you need that - but I don't think it's necessary.

So back to the problem at hand: every package manager I know also lists installed packages when I search for a package. As far as I can see Jenkins plugin package manager doesn't offer a view that has all packages, regardless wether it is installed.

This is quite surprising and should be fixed.