Thank you, everyone, for chiming in. Upon closer examination of the screenshot I provided, I noticed that the “index icon” appeared next to the groups that had been successfully synced with the database, accordingly a correspending folder was created on my Mac mini. Conversely, I didn’t see the same “index icon” next to the groups that had not been synced with the database and therefore did not appear on my Mac mini as folders.
Since I’m still in the exploration phase of DT, I decided to delete the groups that lacked the “index icon,” created them as folders on my Mac mini, and found that they were indexed correctly and appeared as groups in DT.
Perhaps the lesson here is to always create a folder first on the Mac to be indexed by DT, rather than creating a group in DT first to be synced with the database to create a folder on the Mac.
I hope that makes sense.