Memos (or any of the built-in PIM apps, for that matter) doesn't "see" data on an expansion card, so the only option I can think of would be to use a program like FileZ to save a copy of MemosDB-PMem to the card. That will save the entire Memos database, though. And the only way to "see" that data later would be to delete the database in RAM and copy the saved one from the card to RAM (or use FileProg, which seems to be able to overwrite an existing database instead of giving an error message), which would restore the entire database.
(I'm not sure if the categories for the memo database are in the database itself or in Saved Preferences--in other words, if you put that saved database back in RAM, I don't know if you would then have to re-categorize everything.)
An alternative would be to use an app like SiEd (freeware), which can read and create native .txt files on an expansion card and can navigate anywhere on the card. You could save all of your memos as .txt files in folders which would serve as categories, then either divide those folders among different cards or keep them all on the same card in different folders (like a "work" folder with subfolders corresponding to work categories, a "home" folder with subfolders related to home use, etc.).
