Thanks for joining the thread, Hello000!
I understand the need to enable BAS e-lodgement with branch number on their ABN in QuickBooks Online. We're unable to provide an exact timeframe as to when this gets implemented in the current offerings. Rest assured we've lodge a feedback to our team to let them know if the feature you're looking.
Also, you can check the latest updates about QuickBooks Online: New Features For QuickBooks.
Feel free to post your concerns in the Community or click the Reply button for follow-up questions. We'll be happy to help. Have a good day!