Allow a calculation preview to run immediately without the need for any of the prior calculation sources to have preview tables built.
In other words, the "immediate preview" would work from the existing user-accessible tables and the calculation _Result tables, rather than creating new _Preview tables from the sources.
This would have the benefit of the new "immediate calculation" feature, with the added benefit of not actually saving the changes.
Granted this feature would only make sense if either:
1) In single-edit mode, within the calculation after a change, but prior to selecting finish.
2) In multi-edit mode, either within the calculation after a change or after selecting finish from within the Composer, but prior to saving the multi-edit changes or finalizing multi-edit mode.