Are those multiple partitions bootable to full systems, where you can keep files and your own apps?
Or, are they simply bootable macOS installers?
I am guessing that you have multiple installers? (that would be why you mentioned createinstallmedia...?)
reason I ask? I have about a dozen drives with multiple installer partitions, some have all installers from Leopard to Sonoma, all on the same drive (total of 15 bootable partitions for all that). When I make new drives, I do many with createinstallmedia (older installers don't use that command). I do this fairly often--ten times a month, more or less--and only 5 installers would probably take less than 30 minutes to partition the drive, and run the createinstallmedia setup for 5 bootable installers. You could use the terminal command dd to clone each partition to a partition on another drive.