Back in the old days of 2009, J2ME was still popular. And I had LG-GB250. I searched for a text editor and found only jTextLite 1.01 ((c) Malcolm Bryant & FreEPOC 2/Oct/09), but unfortunately it didn't work.
As far as I remember, my (now broken) phone supported de-facto a save operation of up to 2K characters.
Using decompile, I did some modification to make it work. It was never published to anyone else, was just a kind of exercise.