Hi Mark, yup an undo that persists between sessions is something that I've thought about before and that I want to try to implement in the future.

The tricky part about it is that the stored data may grow to be very large over time, and it's just a difficult task in general to efficiently process very large chunks of data. So it's an area that will need to be designed very carefully.

Because it will be a difficult area to implement well, I'm not sure if it will happen during v3 or not yet, but possibly.

I can tell you that it is something that I'm definitely interested in pursuing though.

I think if I can do it properly it may also be a big stepping stone to enabling a deeper history function to work better as well, since one of the parts about being able to apply a history update (like where you edit some of the original curves and then the pieces built from them update) involves having some storage of objects that may have been deleted from the current model, if they were part of the chain of actions that went into building the current final result. A persistent undo store could possibly work as the storage for this kind of purpose in addition to enabling just regular undo functions across sessions as well.

- Michael