In Spacedraw, every construction step can be undone, even after exiting and restarting the application, and with the paid version of Spacedraw, the construction-history of a scene can be saved and loaded in a file. The steps can be displayed in a list, and you can directly load any state from the list.
In principle, any number of steps can be saved; they are first saved to the RAM, and the older ones then moved to the disk (the internal storage); when your device is out of RAM or disk-space, errors will occur. You can enable and disable the recording of actions at any time via enable undos in the F-menu.
Selections are treated as individual steps; the view and the display options are also saved for every state and can be loaded together with the state; therefor, enable load view with undo in the preferences.
to undo the last action, slide into the screen from right over the undo-rim, the green line at the top right border, or tap close besides the line
to redo an action, slide into the screen from right over the redo-rim, the blue line below the green one, or tap close besides it
to show the history-list, slide leftwards into the screen over the undo-rim further, until the list is displayed; the currently loaded state is indicated in green; you can now scroll, zoom or resize the list, see Panels
to load a state from the history-list, tap it; you can “scrub” through the history by touching the active (green) state, and then dragging slowly up/down; if a state takes longer to load than you linger over it, it is skipped
to clear the history, invoke clear undos from the F-menu; all undo information, and the historic painting texture image-files are deleted