In case anyone else bought or built one of these, I did in the end find a very nice, super-simple full screen editor: Simple Kitten Editor, written by a Japanese programmer who goes by the name SkyRiver (@wincp on Twitter)
https://piclabo.blog.ss-blog.jp/CPM68K_SKED
You will need to download the
sked68k_v001f.zip file on the page (all in Japanese but the Google Translated version is pretty good), unzip it and transfer the SKED.REL file over to your board (either using Kermit in terraterm, say, or using CPMtools on the disk image with the SD card plugged into your PC)
Following examples are based on my CP/M system files beingon my A: drive and having downloaded the SKED file to my I: drive where I keep 3rd party utilities. My H: drive (Home) is where I have my programming source files.
Once the file is over onto the 68K-MBC disk and it is running again, run:
Adjust paths as required.
Then just type , eg:
If the file does not exist it will be created.
CTRL+J displays the help with all the Key combinations.
Hope this is of use to anyone playing with these great little boards.
a.k.a. Jean-Yves