Well, sometimes the problem is located between the chair and the keyboard - at least a little.  🤦‍  Using the disk imaging function of the backup software (essentially "diskcopy" the HD/SSD) was a non-starter, literally.  I finally made a backup of my desktop's SSD to a third drive (a portable SSD in this case) and then restored the backup to the Optiplex 7060 USFF's SSD.  Success!  The 7060 booted from its own SSD, and presented me with my usual working desktop view.  I've since removed many gigabytes of software that will remain on my "heavy work" desktop, but not on this smaller desktop that I have been using for daily driver tasks such as emailing, light document creation, and of course web surfing. Thanks to all who responded!
I image copied (cloned) the 500GB NVMe boot drive from my desktop to the NVMe boot drive in my 7060 USFF.  I cannot get the 7060 to boot now, despite changing a number of settings in the BIOS of the 7060 that seemed relevant. Any ideas? -OP
Dell Optiplex 7060 USFF won't boot from imaged NVMe drive