Auto Save in Web Process Designer saves your process flow automatically, in specified intervals, as you work. You can enable the Auto Save and define the specified time interval by changing the value of the property.
You can use the Autosave 
toggle button from toolbar to on/off Autosave feature for the current tab. If you open a new process flow, the default property of Autosave is applicable.
You can also see the last saved details in toolbar.
By default, Auto Save is enabled. However, follow the steps below to update the property of Auto Save.
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