I have some 32-bit apps I wanted to retain access to, so it was time to virtualize Mojave under Monterey. I found these excellent instructions, hopefully they help you too:

https://www.whatroute.net/installerapp2iso.html

Of course I installed VirtualBox Extensions in the middle of this and somehow needed to follow advice at these links:

https://stackoverflow.com/questions/65149373/kernel-driver-not-installed-rc-1908-getting-errors-in-macos-big-sur-11-0-1

https://stackoverflow.com/questions/41691803/how-to-install-guest-addition-in-mac-os-as-guest-and-windows-machine-as-host

And note to self and others who arrive here, as of today I do not recommend instructions in the following two links as they did not work for my set up:

https://appletoolbox.com/need-to-run-32-bit-apps-on-macos-catalina-use-a-mojave-virtual-machine/

https://forums.virtualbox.org/viewtopic.php?t=95049

So far things are working well. If all of this virtualization should later fail and I’m unable to continue on with my previous work in the app Addresses & Labels, I vow to follow others’ advice and give this app a shot or maybe even consider gLabels through macports.

Also, for those coming here for the first time, maybe consider skipping all the steps above and try this instead.