Hi All, finally got it to work! I followed the guide djileviticus first listed (on 10/08/2021) but had to improvise slightly:
A. After step 5 it's important to make sure NEITHER 'Load Options' or 'Save Options' are ticked.
B. After clicking 'Start RAMDisk' (step 6) a new drive was created on my PC (H:/) as seen in Windows Explorer
C. I copied the entire ZXDS folder from my Flashcart (that works in DS/DSi slot-1) and pasted that into H:/ drive (step 7)
D. Then continue from step 8 (and in step 9 named the file ZXDS.img)
E. In step 12, as well as setting 'RAM disk' to 0, I also set 'Run in' to 'DS mode'
So far as I can tell, all game file types that work from slot-1 flashcart work from this method and game titles don't need to be in upper case or limited to 7 characters. Also, WiFi link-up works for two-player games (Match Day II anyone?!) and the load/save slots can be used. Basically, everything works like on flashcart. (The only thing that I still can't get to work is online game
downloads. This works on my 2DS XL using ZXDS 2.1.1 but not on DSi using ZXDS 1.3.4. Has anyone managed to get it to work, on DSi)?
Thanks very much for the help from banjo2 and djilevictus. Great to have this working from SD card
Edit: just noticed that whilst ‘save slots’ can be created, once turning DSi off and then back on and reloading ZXDS, the saves disappear. Wonder if they can be made permanent?