I don’t think it totally answers your needs as it’s modal, but have you found the full-map-zoom shortcut Cmd+Opt+Ctrl (here)?
While the keys are depressed, the view zooms out to show the entire map, and returns to previous zoom/location when the keys are released.
A navigator style window, with the whole map and with the current viewed area as a draggable cursor has been discussed in the past but I don’t know if it’s a feature. I find that once maps get really large it’s generally time to switch to discrete maps (nested or otherwise) or simply use Outline. In saying that I totally get that unless all notes are on the same map you can’t see link lines - if that’s a key reason for your use of map view.