GadgetBridge suggestion

What is the thing you want to achieve, disregarding the technicalities?

I think the request is mostly clear
"additional feature in GadgetBridge that lets me enter a line of text and directly send that text to the watch."

I understand it like some textfield somewhere in GB where you could directly enter e.g. require("Storage").eraseAll();E.reboot() and watch is immediately erased and rebooted. Or maybe something more practical and less destructive is an option too :-)

I think this is related to another previously mentioned feature - to have REPL console output available in the AppManager/Apploader in GadgetBridge. The "More .." tab has lot of advanced functionality so this could be there too.

What I am trying to achieve is the ability to send configuration data to the watch in the absence of an internet connection that gives me access to the app loader.

The italicised text is the key item here. There are times when I wish to modify the configuration data for my watch face, but I do not have an internet connection available. Under these circumstances I can't use the app loader, so I need to do this locally.

I could solve this by writing a custom Android app that sends text to the com.bangle.uart.tx intent, which would allow sending a line of text to the REPL. However I'm guessing that 99.9% of the work is already done in GadgetBridge, which means it might be a relatively quick and easy change.

If not, then I'll just have to write an Android app which will allow me to get where I want to be.