Right-clicking on the "Save" 
icon displays the "Snapshot" function.
The "Snapshot" function is designed to save different versions of your editing session every "x" minutes automatically.
This way, you can reload an edited version.
To reload a previous version of an edited session :
Right-click on the "Save" icon.
The "Load Snapshot Save/Charger a Snapshot Backup" window appears.
Select the version to reload.
Double-click it or click "OK".