kdocker

home page https://github.com/user-none/KDocker
old homepage with a bit more info and screenshots: http://kdocker.sourceforge.net/

Should be included because it lets you dock any application to tray, for example 'kdocker corebird' or 'kdocker -i /path/to/icon.png corebird'
there is nothing like this currently in the repos
Despite the 'K' it works just fine in gnome and probably budgie as well, in addition to kde

yes its open source (GPL 2.0)

ive used it for years on other distros, i find it extremely useful. not sure how many would use it though, perhaps a few if they knew it existed?

link to most recent tarball: https://github.com/user-none/KDocker/archive/5.0.tar.gz