Recently Libre Writer places the working screen far to the right of the Libre screen

Is this a Writer setting that I’ve messed up?
When one opens a doc one sees a blank grey screen, the desired one is off to the right.
Calc is OK.
I am on a Mac with OS X 10.15.4
Using Libre

You are in “book-mode”: 2 pages side-by-side, odd pages at right like pages are presented in an opened book.

To return to single-page mode, click on the “single-page” small icon near the zoom slider in the bottom status bar:
zoom control

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