Sounds like you are talking about Export Audio Mixdown, not Bounce Selection? (Nuendo nomenclature is not ProTools’ thank goodness)
If you mean you want a default Export Audio folder it should not be called “bounce files”, please. I call my mix down folder by sample rate and our studio name.
If you mean Bounce Selection: I would prefer an option in Preferences that would enable a System Folder Dialog box to open when we Bounce Files. So we could select or create which system folder we want to bounce to instead of the default Audio Folder. Uncheck the preference and bounce defaults to project audio folder as it always has, no extra clicking. Most often I bounce stems to send to clients or producers. It would be a huge advantage to be able Bounce Selection, have a dialog box open to create a system folder named Producer Name. Then simply send that folder to the producer. Clean and quick.
Nuendo is great,