It works, but... there's no way to use custom download locations, because /Downloads (my default location on Firefox under Debian Linux always is chosen.
That's a bad habit, because very often I use custom storage locations like USB HD's and especially bigger downloads put a high load unnecessarily on my SSD, which otherwise could be re-assigned completely.
Furthermore this AddOn seems to be dead, as there was no update since 2 full years... and there are numerous open tickets visible.
To clarify: I will re-edit this review in _ a n y _ case (dead or alive) and will downgrade it in case of a dead project and no response, so that it becomes at least obvious, that one should consider to remove this more and more function-wise dying thing from Firefox.