From what I've heard, Lotus Improv (1991, failed 1996) was intended as a spreadsheet where each data set was stored in a separate namespace/object/table, which had named columns/rows, or even more than 2 dimensions. Apparently Quantrix is a successor used in the business/financial world, but is unfortunately not free or open-source. That's a shame, as I want something of that sort for casual scientific computation or statistical number crunching. Maybe I can use Python pandas or R dataframes, but spreadsheets have the useful trait that they're functional and side-effect-free, unlike scripts or notebooks.

Sounds like Access which always felt to me like a stepping stone between Excel and SQL Server with Visual Basic. My guess is that's what Microsoft has in mind anyway

You mean turn it into a different tool called Access or formerly FoxPro?

I see. Iirc, Access was too much developer-oriented last time I checked it around 20 years ago. As a developer you can just step up and try to take control, but users have no such courage. If excel merged parts of access later into a single product, suggesting, but not forcing users to maintain at least a partial scheme, then maybe. Sort of in-place gradual migration without “work here or go back” next morning ultimatums.