Finally, I took a different approach.
I realized that the 500 GB disk-drive in the computer was manufactured in 2017, making it over 6 years old, and thus was greatly out-of-warranty, and that the "C:" partition was nowhere near full.
So, I purchased a 500 GB SSD (SATA), and used disk-cloning software to copy all the partitions. The software allowed me to slightly shrink the "C:" partition, by less than 1 GByte, during the process of copying the partition. There was no need to "shrink" the "C:" partition on the 2017-vintage disk-drive, and thus no danger that a "shrink" might have gone terribly wrong on this "production" volume.
The "recovery" partition physically followed the "C:" partition.
Although the Windows "Disk Manager" incorrectly reported the partition as "0%-used", the software I used correctly reported that the files occupied about 400 MBytes.
While copying the "Recovery" partition, the software allowed it to grow in size to consume that new disk-space.
When I booted from the SSD, everything was fine. The new "recovery" partition uses less than 2 GB (out of the 500 GB).
One note: there was one cluster of sectors on the 2017-vintage disk-drive that could not be read by the cloning software. The software identified the file that "owned" that cluster, and the software allowed me to "continue" with the cloning. Obviously, Windows never was using that inaccessible file. So, its "loss" is not a problem for me.
Due to the new SSD disk-drive, Windows works much faster. This is a bonus, and I also have the 2017-vintage drive labelled as "full backup in March 2024", should I ever need it.
Done. :-)