Keep in mind for the following comments that I haven't had the Studies app installed on an iphone for about a year, and I reset the cloud on both apps right before deleting the phone app. :

When the mac app is installed for the first time, the there is long single subdirectory of ~Library/Containers/Studies/Data/CloudKit/ that looks like a SHA named '7c...'

As time has gone by, a number of similarly long named subdirectories have accumulated that are siblings of the original '7c...'. Seven of them. A couple of these also have counterparts created in the ~Library/Containers/Studies/Data/Library/Caches/CloudKit/ folder, but most do not. After their creation, the activity of the app is still taking place within the original '7c...' folder and its subdirectories, with one exception. Most recently when I signed in and out of my Apple ID, the two most recent siblings of ~Library/Containers/Studies/Data/CloudKit/'7c...' were created when I signed back in. These two each have a 'Records' subdirectory with pcs.db-wal, pcs.db, and pcs.db-shm files. These files in both of these Records directories have continued to show a change in the Date Modified timestamp each day when an internet connection is established (even though the app has yet to be opened). Not sure what's up with that. But other than that, all these other folders I mention that have proliferated over time appear to have ceased being relevant, not having any activity.

I learned that signing in and out of the Apple ID on the macbook will do it.
****But do you know what kind of things trigger their creation? ***

There are other relecs that I may need to manually delete, such as the Assets folder inside ~Library/Containers/Studies/Data/Library/Caches/CloudKit/7c... that has about 70 files (no file extension, but type Document) totaling 49mbs in it, all with Date Modified from about a year ago. These appear to be a relec from the last attempt to sync with the iphone app before I perform a reset on both apps and deleted the phone app.

Also, in the Documents/Studies Backups folder I have the three most recent backup folders that are to be expected. The there are also two zip files around 45 mb each that have Date Modified timestamps of from September and August of 2021. I want to start cleaning up this mess. I can't see it will be a problem to delete all of these since I have a copy of the Studies library folder saved elsewhere as a backup if needed. Then I'll just allow the new backups to be created as they normally do going forward.

In your testing, have you seen this added folders such as I have mentioned accumulate like this?