I got this to work, & for future reference for anyone else who wants to know how, here's how I did it:
-I have the original wallet containing 'Account-A' that I created when I first installed BitSharesX backed up to my hard drive, & I created a staging directory elsewhere where I'll keep a current version of each account's backup under directories titled 'Account-A' & 'Account-B'. This since the actual backups have the same name, & I dare not mess with renaming them in case they wouldn't be restorable without remembering their exact naming originally.
-I uninstalled the BitSharesX application, & afterward deleted the BitSharesX directory from Users/Username/AppData/Roaming.
-Then I ran a registry cleaner app for the sake of completeness in case there were registry settings left over from the uninstaller. I don't think this step was necessary, though.
-I then reinstalled the BitSharesX application fresh, & created the new account following the prompts.
-I backed up the newly created wallet containing the new 'Account-B' to its own directory, then copied that backup to my staging area where I keep current versions of each account's wallet.
-I can now 'Import' each separate wallet, each containing a single account, to effectively switch back & forth between them.
One question remains, however:
During the wallet import process, there's a message saying 'This will backup and replace your current wallet!'.
It's unclear to me where this particular backup gets saved, as the following screens don't ask for a file location to save it at. I checked the timestamps on the backups I already had after I imported back & forth a couple times, & it didn't appear to overwrite my current backups, so it's not using the 'last used' manual export directory.
I wouldn't know how to utilize that particular backup had I needed to, but it doesn't matter in my case since I have manual backups exported to my dedicated backup location.
So no worries about that.
Hope documenting this helps someone else.