It was that wat i was looking for, but unfortunalety i can't see it...grey on grey won't work. On a dark Skin it disappears.
Can you consider to make a version with diferent colors? white icon on dark grey ...or is there an option that i can do this by myself?

i simply use FF Dark Mode, what looks quite good.
but:
after restart of FF 65 B11 it appeared white...before it was greyish und unvisible...will rate you 5 stars.
only i don't understand this :-)))