Thanky you for your answer.
I tried to copy data using mentioned workaround and it worked well to copy boards, or after minor change even Cards, which is even more usable for me. However, without original details, like date created, members, labels or checklists. I can imagine, that via Advanced options it is possible to import such a details. Do you have any idea, where can I find explanations for Expressions?
THX
MH