George Fagg wrote a Word Processor called TENTEXT. It was submitted to ACU as a 10-Liner BASIC program completely poked to memory from UUEncode. It was in the Oct 1991 issue of ACU, probably the easiest way to find it is on NVG in a file marked ACU91.ZIP, that archive will have 2 DSK images in it, more likely being in the ACU91B.DSK, the file is called TENTEXT.BAS
Unfortunately I don't know if the program will return you to BASIC or not, but @Nich seemed rather impressed with it.
I found that with google's help.
WOW, what kind of cool BASIC-Poker is this
It's a slim and fast texteditor, strange is the save-format (BIN instead of ASCII), no return to BASIC.
I think, this would be my approach, to disassemble this editor an change the needed parts.
(Plan B's are Protext and Prodatron's sources)