Every single project I open in Mojave with 10.5.X (since launch) forgets what is happening on the second screen.
My setup with Cubase has always been two screens - the mixer on one and project window on the primary.
The maximised mixer window used to always remember the fact that the mixer was maximised and on the second screen. (At least since I can recall from the early 2000s with Macs).
Now with 10.5 and Mojave I have to move the mixer up there to the second monitor every time (and it NEVER remembers).
I am not using workspaces and never have.