Here's an excerpt from the Discovery Studio Help pages that lists all the shortcuts to use in the Graphics View of the Molecule Window. The page can be found in the Help under Working with Discovery Studio > Working with the client > Mouse and keyboard actions

Learn these by heart and you'll be exploring the ins and outs of your favorite protein/ligand complex with ease.

Note, there are other useful shortcuts under that Help page such as mouse/key actions to control the Sequence Window so take a look.