Obviously, the expected behavior would be for Dorico to remember the Zoom setting in Write Mode (just as it remembers the fact that I was in Galley View) (sorry if this is an already-discussed bug, etc.?)…
When you switch from page view to galley view, Dorico will try to keep the selection in view if it can, but depending on whether or not it’s kept the view hanging around, it may recreate the view at the default zoom level defined in Preferences.
Excellent. So the solution (if I’m working actively in Galley View) is to change the default view in Preferences to something like “Galley View/100% zoom” and it will go back to this default if I change Modes and then come back to Write Mode.