When I went into this I was thinking we will have a concept of calculated columns and a calculated row (like option of "sums/avg/...") row at the end.

Now the default mode of operation is spreadsheet as immutable data. So it's not really reactive, but it's still declarable. I am open to renaming it to "table", but I also want to first see where the mutable (spreadsheet as state holding structure) part brings me. Thanks (and also to the similar sibling comment).