Need Boot Manager at startup every time. (old question, new problem)



I need the boot manager at startup every time. I have a 2014 mini with 2 bootable partitions. Yosemite on one and Catalina on the other. Obviously, need to run legacy software.

When running Yosemite, the Catalina drive doesn’t mount. So it can’t be selected as the boot disk from within Yosemite.

The wireless keyboard doesn’t interrupt the boot sequence for keyboard shortcuts to work.

Haven’t found a third party boot manager to work in this setup and a wired keyboard doesn’t suit the workspace.

I have the “sudo nvram manufacturing-enter-picker=true” saved to a text file. Too much to explain to the user,”open terminal, cut, paste, etc.”

It would seem that this would just be a line written into a file but which, where, how?