First off all, I don’t know exactly where I should post this thread. (Gmod13 or workshop) Because it’s both.
If you cancel a subscribtion via the workshop site the Addon stays in the installed addon list. Of course, with an green “+” at the bottom left edge of the icon.
I think it doesn’t deinstall, too, but the fact that it’s still in the list means there something wrong.
What causes this:
Now, if you click on the green “+” of the Addon, which generally means you want to install it. It will download it again. Remember, it IS already in the installed list.
So, if you want it to be removed you have to wait, until the download is finished, because if you click on the red “-” before it is finished installing, it won’t be deinstalled, but removed from the installed addons list. (It will be installed, without it being in the installed list.)
What should happen:
If you cancel a subscribtion via workshop site, it should deinstall and remove itself from the installed addons list. The same as if you would click on the red “-”.