K9 and Pixel 4a badly broken

Long time, very happy K9 user on 4 or 5 phones. Decided to move from Pixel 3a to 4a, knowing that the 4a is new. Oops. After many install/uninstalls I managed to get one account working - at least it receives mail. The biggest problem and killer is the top-left/bottom-left back navigation arrows are missing. Makes navigation difficult. Also, forward nav buttons like “Next” sometimes don’t work.

Importing settings from previous phone: I put the k9s file in half a dozen folders but K9 didn’t see them when I navigated to them. I admit I don’t know exactly where to put the file. Have done it successfully on earlier phones.

Using version 5.600
Questions? Suggestions?

All is well. Found in the phone settings that I could turn on a 3 button nav bar at the bottom so the back button is back. The Pixel 3a (usually) has 2 Back buttons, one at top-left and one at bottom-left.
Regarding importing settings, today the file manager found the copy I put in Download. Had also put it in 4 other directories but they weren’t found. Finding one is good enough!