Just checking: ephemeral DataStores are on the roadmap, which allows temporary data storage. No details have been provided on the feature thus far but would this hypothetically resolve or help your use case? I can imagine what it might entail when it goes live.
I’m wagering guesses here since there’s no information on the feature so far, but it does sound self explanatory. I doubt that it’d reset on its own so it’s not exactly temporary in the sense of “until the session ends” but temporary in the sense of “expires after X amount of time”. It depends on how fast you enter and exit Studio test sessions though, TTL might not be an appropriate alternative to session-only data (or just entirely a non-solution).
If that’s not helpful, then I know buildthomas created a module that can emulate DataStores in Studio but use DataStoreService for live games, so essentially there’s little to no work needed on your behalf for switching between testing DataStores in Studio and performing actual data reading/writing in live games. That’s available at MockDataStoreService.