Thanks for the suggestion. This solution Affinity Publisher offers is a little bit awkward, but it worked.
But how would I solve this problem:
I want to print a kind of birthday card by folding a sheet of paper A4 twice to get a 4-page card A6.
Please see the two attached pdf-files. (Red dotted line A = first fold, green dotted line B = second fold)
How would I do the printer setup in Affinity Publisher? (Good old Corel Draw offers a very simple solution for that in their page layout setup)
Folded Card 1.afdesign
Folded Card 2.afdesign