The 423 build fixed the notation window issue for me.
I have a 2020 MacBook Pro w Big Sur 11.2.3
I got BiaB 2020 for Mac yesterday. ( Xgrade from Windows)
The notation window was blank,
Today I found this thread and downloaded build 423 from the link and the notation window works.

Edited by Gubben i Ladan (04/09/21 07:45 AM)
Edit Reason: typos
Gubben i Lådan