Arkio models are automatically saved as edits are made and a per session undo/redo history is stored. Undo and redo are controlled with the left controller. Undo is triggered by clicking on the left side of the touchpad or moving the joystick left, and vice versa for redo.
Undo/redo is possible for all modeling actions but not everything in Arkio can be undone - deleting a saved model from your carousel is a good example. Opening a new model on the carousel will reset the undo/redo system so only actions done after the opening can be undone.
When moving from a single user to Multi-user meeting the undo/redo history gets transferred to a global Undo/redo history for that scene. That means an undo from one participant can undo a modeling action just finished by another user. This is also true for undo/redo and modeling actions done e.g. on an iPad.