How do I set the on-screen zoom level in OS X TextEdit?
The following workaround does at least provide a fixed user-settable zoom (TextEdit 1.13, OS X 10.13.6 [High Sierra]).

Create and save a blank TextEdit doc (maybe make it Stationery via
Finder Info)
Open the doc in TextEdit (don't use &quot;Open Recent&quot;) and
select the Option button to &quot;ignore rich text commands&quot;. (Or, open it
in some text editor which doesn't do RTF.)
Add the command \viewscaleNNN in the header material; or,
preferably, the command string \margl1440\margr1440\vieww16140\viewh20440\viewkind1\viewscale140

This does the following: set the left margin to 1 inch (1440 units, whatever they are), the right margin similarly, the window width and height to big enough that the doc will open showing a full page (otherwise you get the middle of the page but not the edges), the &quot;viewkind&quot; command (use 1 as shown for Page Layout view, called &quot;Wrap to Page&quot; in TextEdit), and finally the viewscaleNNN command, with &quot;NNN&quot; here being &quot;140&quot; setting the zoom to 140%, which is what is needed on my particular setup; experiment to find the percentage you like. These and many more RTF commands may be found here.

Finally, save the doc and use it as stationery.