Sorry for not getting back to you earlier.
I’m not 100% familiar with this area, but I believe–from memory–that the deletion of n+1 snapshots is based on the snapshot name. As a result renaming the snapshot may help but I would express a lot of concern about doing so and would thus not recommend doing it. Indeed, that would likely create a disconnection between what Rockstor should see and what is actually present on the disk and thus open the door to a lot of misbehaviors.
Alternatively, there is the option to create a snapshot manually (outside of a scheduled task, see documentation) when you want it.
Good question… I too would love to be able to see that. There was a lot of work to implement Snapper a little while ago, which may help (or at least facilitate) to do just that.
The base code of Rockstor changed a lot since then and it would thus most likely need a lot of work, but the incoming move to openSUSE should hopefully help with that as well.
Other users here may most likely have better ideas on how to see changes between snapshots, however.
Hope this helps,