Matt - I had previously created a Playlist called 'H Drive Reconstruction'. I populated it with missing files and the files I was restoring from the cloud, then when a missing file was restored, I deleted the originally missing files and removed their replacements from the Playlist. That left me with a list of missing files I still needed to restore.
Now, when I'm working in the main library and go to the tree to open the Playlist, MC hangs for 2-3 minutes (sometimes indefinitely), and if/when it reopens and I try to remove a restored file from the Playlist, it hangs for up to 3-4 minutes before completing the action. Ditto, when I try to delete the missing original from the Library.
If I take the same action to delete missing files that have been restored in the main library, the deletion occurs in a matter of 2-3 seconds.
As I said, I've figured out a workaround (a little clunky) but wonder why there's such a difference in response time.