Is there a way of replacing text (eg ‘< br >’) with a newline? I tried \n and \i but that didn`t work
This can’t be done with the regular UI, but you can use this Shortcut. Replace the note identifier on top with the one of the note you want to edit and the text to replace <br> if needed.
Thanks, but when I click on the link in your reply, and then on the Get Shortcut button which appears, I am sent to the App Store download page for the Shortcut app, which I already have
Works like a charm here, added to my library of Bear shortcuts 
Ah, OK. It worked when I used my phone not my Mac. Thanks!