I just run Karaoke twice a month in the senior living where I live. I also run kJams in my apartment for my own amusement and practice. In my apartment, I don't need separate monitors. Right now, kJams works for me in my apartment, with the data files on my *real* drive, and the executable on my virtual drive. It doesn't yet work for me when I take my iMac downstairs, as the VM doesn't see the separate monitors.
Your reply seems to be telling me that if I had dual boot, I could run it the same way. kJams allows me to have 2 copies. I used to have the backup copy on my wife's computer, but now I have one on my VM and one on my real computer. I could set it up to have one in the VM, and one on the Mojave partition, with the data on my Catalina partition.
This helps me decide what to do with my hardware. Right now I have a late 2013 iMac with a 1TB fusion drive with less than 200GB free disk space. My wife is talking about getting me an upgrade for Christmas. I'd sort of like taking a rain-check until the next iMacs come out (which I expect will likely be nice upgrades). But getting a new iMac for Christmas with a 2TB fusion drive and dual booting may be the better solution than waiting until mid 2020 for the kJams and iMac upgrades. At least it is a workable solution, and it may be a solution my wife likes better.
Now, if I could find an adapter to enable me to plug a Thunderbolt-3 disk drive into my Thunderbolt-1 Mac, I could buy a Thunderbolt-3 disk drive and dual-boot into it. But I don't want to buy a Thunderbolt-1 disk, and I can't find such an adapter.