sometimes I use smaller noteheads but the key-signatures in front of the smaller noteheads keep having the same size than with bigger noteheads.
Is there a way to change that without creating a new set of noteheads with smaller key-signatures?
if not: wouldn’t it be a nice feature for further versions that the key-signatures change together with the notehead sizes?
I don’t believe there’s any link at all between the size of noteheads and the size of key signatures, so creating a new set of noteheads would not, and could not, achieve smaller key signatures. If you edit the Tonality System (right panel, Key Signatures/Tonality Systems/Accidentals section) you can shrink the size of accidentals in key signatures, I suppose.
Thanx for the idea Leo…hmmmm…that would be a very tricky workaround - not sure if I wanna go into it 
It’s not tricky at all - you just shrink the sharp once, and the flat once, then hit OK and add perfectly ordinary key signatures. Is it actually just smaller staves you’re looking for? If so, you can achieve those by right clicking on any stave (or any element on any stave) and going to the Staff Size context menu.
Ok, cool…I’ll check it out. Thanx again !
very easy indeed it is…works smoothly…thanx.