Save Rows allows users to select a row in a message and save it for later use. The saved rows can be dragged into other messages across any campaign that contains an email channel.
Look for the Save icon on the action icons when a row is selected:
The same action is also available in the row properties panel when a row is selected:
Clicking this icon will display a save dialogue which you can then enter a name for your row and click to save:
Once a row has been saved is can be found in the Email Builder in the Rows tab under the Saved option: