Here is a test build by
alanswx that I've been testing recently,
adding a second floppy drive and the ability to save disks in .nib format to the SD card!
I was able to play Adventure Construction Set and Ultima II with it so far.
It needs disks to be in .nib to write back to them. This is an acceptable trade-off since this is not a copy-protected format anyway; and it also helps keep your files tidy on your SD card e.g. all saves in a separate folder. I would also recommend preparing save disks in AppleWin first since it formats and copies data much faster than MiSTer (which operates at original speed).
To help using the Apple II core with this I started making an archive of .nib save disks ready for use.
For example, I added four "save slots" for Ultima II by making a player disk and duplicating it before creating a character.
What are your favorite games and which save files would you like to see added to this archive?
Files: