In my quest for more screen real estate, I've found many apps that will hide the status bar and even navigation keys, but all of them shut down access to the keyboard. But this one:
https://play.google.com/store/apps/details?...de&hl=en_USdoes the job and allows a functioning keyboard at the same time.
You have to send a WRITE_SECURE_SETTINGS permission and you can do that through adb if you're not rooted or through termux, etc if you are rooted. I'm rooted so I can't personally vouch for the adb command. It's explained here:
https://github.com/rascarlo/GranularImmersiveMode/wikiOne of its many features is that you can go full-screen only for specific apps. I set it up for TextMaker HD and HanDBase. The status bar is hidden, the screen is full of nothing but the app, and the status bar can be pulled down if you need to check something. It will retreat on its own in 3-4 seconds. You can also get rid of the navigation keys if an app doesn't need them.
I was surprised at how many lines of text I could get on the screen with Granular and setting the TextMaker HD font to Arial Bold 12pt and line-spacing to 12.4pt (single space is 14.4pt). Ctrl-Q will close TM so I don't even need the nav keys.
Well worth 99 US cents,
Jake