swipe keyboard code crash on back button

However, I've found that the textinput-file actually do get updated with my code anyway, just reload by holding the side button as usual and test the keyboard again. So the error message feels redundant?

You have Load after saving set as the default of Load the file just written in the IDE - so Espruino is trying to load the library you just wrote as if it's an app - which is why there's the error.

It could of course try and guess whether you're writing a widget, boot code, library etc based on the filename but that feels like a minefield