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PS: I'm still looking into doing a rewrite that uses IndexDB instead of Greasemonkey values to store data but I sort of forgot about that one :). Maybe next season...
FYI: Firefox Quantum had the devs of Greasemonkey update a lot of things in their extension. Currently the script will only work with Tampermonkey. I'll try to fix the compatibility but since I don't really know what I'm doing anyways it will take me some time.