FYI, using 2015 iMac with OS 12.5.
Just downloaded and opened DT 4.0.0. I tried to open an image in second monitor window, and clicked the green button to fill the screen (full screen, not zoom). I can no longer exit the full screen without quitting DT, as the top bar of red/yellow/green simply does not show up when hovering over the top of the full screen window.
IIRC you just need to click back on the icon used to open the secondary display.
Pascal,
for some reason, the 2nd monitor on my Mac opened on a 2nd monitor…on a different desktop setting!
So I navigated back to the desktop that was running DT, and clicked the icon…worked.
Now to figure out why it keeps doing that, even though I have assgined DT to a single desktop.