If you would like to access a previous version of the design you are working on, you can find it in the automatically generated revision tree. The revision tree can be found near the save button, at the top left corner of your screen. It is the icon with the 3 branches. If you have the autosave function turned on, a version of your design will be saved every 5 minutes. Otherwise, each time you click the save icon, a new revision is added to the tree.