Yes. You can do that by either dragging the folder into the workspace section or using the menu above the tree (cog icon) and select "Add folder to workspace". This is essentially like a bookmark or favourite in Finder. 

The great thing is, you can even do that for removable drives/sd cards and when you disconnect the drive, the bookmark will remain in the workspace tree and become disconnected and then become reconnected automatically once you reconnect the respective drive.