hi Oliver, I think there is nothing to do in the freeplane package, because I think its mime type config makes sense (see above)?
Regarding the cinnamon file manager: Can you see whether there is configuration in ~/.config/**? I think removing that is the best way to reset your settings. BTW: you can just reply to this bug, no need to create a new bug report (even if that is the same bug - how did you create this?) Cheers and Best Regards, -- Felix Natter