I'm glad to tell you that you can now go back to an older version of a saved music score document.
When you browse an older version in your document history, you'll now see a blue bar with the revision details and a link to start again from this one (Revert to this version).
When reverting to a saved version, the current modifications will be saved in the history, so you can revert again at any time you want.
Hope you will enjoy this new great functionnality.
See you around,
Photo credits: CC-BY David Michalczuk