Edit existing message
If you're looking for a high-level method (where it automatically uses the user's configured editor, etc.) there is no such function. You can however load the message's text (using the MsgBase class) into a buffer, save to a file, then use the console.editfile() function to edit the contents, load the file contents back into a buffer an duse the MsgBase class to save the modified message body.
It's probably not worth the effort. :-)
The C++ method that would need to be exposed via JS (and isn't) is sbbs_t::editmsg() and it wouldn't be trivial to do since it needs an open message as an argument. I'll add it to the to-do list however.
digital man Snapple "Real Fact" #73: The average person spends 2 weeks of it's life waiting for a traffic light to change.