You can group accounts to get a consolidated view.
You could also export all your transactions, masage them outside of PP (if necessary), and then import them back in to the desired accounts. But then you’ll have duplicate transactions for the same security (in separate accounts though).
Thanks for the fast response! Yes, you brought the right answers, but the point is that I have a depot at a first and a second bank. I’d like to merry them at a new bank. For simplification, it would be great just to bring the two into one new account.
You could also do it with a rebooking (not sure how it is translated in PP, in German it’s Umbuchung). Than you will still have the history in PP. If you don’t want to have it, you also just could edit the bookings and select the new account.