How to Rename Drives in Startup Manager?

I run different versions of MacOS on my iMac in different APFS volumes on my internal drive and on an external SSD. I have no problem naming the volumes to reflect what is on them using Disk Utility so they show up correctly in the Finder, but the Startup Manager which you get when you hold down the Option key will not change and keeps using names that were set when the drives were formatted.

Does anyone know a way to change the Startup Manager volume names without reformatting?

Question: Are these different volumes in the same APFS container?
What does the Startup Disk preference pane show?

On the internal drive, there are 3 volumes in one container, on the external ssd there is one volume in one container.

Startup Disk preferences shows the same thing as the Finder, using the names I gave the volumes via Disk Utility. It’s only the Startup Manager as far as I can tell that will not use them.

For further clarification: what, specifically, are the names that the Startup Manager is showing, and what are the names you have given them?

In Finder my SSD says Big Sur, but in Startup Manager it says OWC 1. Similarly for the internal drive I have named volumes Catalina and High Sierra, which Startup Manager calls by their old names Mojave and Catalina Backup.

My guess is it’s showing container name instead of volume name or something like that. If you posted a screenshot (redacted) of your DiskUtility window that would probably clarify.

The container names are totally different, e.g. Container disk 1, container disk 4, and do not appear either in the Finder or the Startup Manager.

There’s a long discussion of what seems related here:

You might also check the discussion on Tidbits-talk concerning renaming boot drives.

Thanks Adam and Alan. It looks like renaming things in the apple startup manager is not possible without reformatting. Does anyone know of an alternative startup manager for MacOS?

Strangely all but one of my Startup Manager volumes have now changed to what I wanted them to be after I booted the iMac once from the external SSD. I guess for that one I would have to reformat.