Hey!
Finally I found a text editor software, NoteTab Pro, which can help to edit and save TXT files for Midjay or any other Ketron keyboard.Doesnt do that itself but under menu/modfied/Lines/Reformat lines you can adjust characters number and also because of text lines numbers you may have an ideia of how many lines per strophe BTW.
I'm using 9 lines with 30 letters for each page in Midjay.
Hope it helps!
Vio