GadgetBridge suggestion

There are times when I wish to modify the configuration data for my watch face, but I do not have an internet connection available.

So you do literally just want to send JS commands over to the watch, nothing else?

If so, I'd say you should go to https://www.espruino.com/ide/ in Chrome on your phone, and click the Install button on the prompt that comes up and it'll create an icon on your phone's home screen. The IDE has been written such that it's a PWA and even though it's a webpage it can load everything it needs to run offline into your phone's memory - so once you've been once and installed it (I think even if you haven't installed) you can use it when your phone is offline (even though it's using the web browser).

So to use it, just disconnect Gadgetbridge from the watch, load the IDE from the Android app list and connect. And now you get a terminal, syntax highlighted text editor, access to read/write storage files/etc.

While somewhere we could add a text box to Gadgetbridge, the immediate question then is what about a terminal so you can see what the response is. Then maybe you want a syntax highlighted editor, access to files, etc and before we know it we've just reimplemented the IDE.