The undo stack should persist across application openings.
The problem that this feature will solve:
As it stands, productionising a model is oftentimes a two step process: assembling a model from sub-objects, and then union-ing everything together and applying various chamfers/fillets/radii to join points.
If you accidentally exit the application/it crashes/it restarts itself overnight due to an update when your model is “glued together”, you then potentially have large amounts of work to disassemble the model again (or you have to restore from a backup).
Brief description of the outcomes that you expect from this feature:
Maintaining the undo stack on a per-model basis across app restarts would solve this. Note that sometimes users will hold down “undo” until it stops undoing, to “revert” a model. If the undo stack is persisted, there should be a warning before moving past the point in the stack at which the model was opened, to avoid accidental loss of work.
The corollary of this is that until such a feature is implemented, Shapr3D should NEVER automatically restart itself or log the user out without user intervention, because doing so poses a real risk of data loss.