Quick key to switch from Filmstrip to Essentials?

Hi @Hansenphoto9983422, yes you can, but there are minor conditions. 

The catch here is that you need to arrange your Workspaces. My essential workspace is "Gary's Workspace," and I've always had that at the front of the list. What you need to do, though, is to arrange your two (or more) desired Workspaces in order for at least the first five.

To do this, go to the end of the workspace list and look for Edit Workspaces

 Once there, you can change the order by dragging them up or down. Look for the blue line because that's where the workspace will land. Below, I'm moving the Metadata Workspace to below Output.

Lastly, open up the Keyboard Shortcuts near the bottom of the Edit menu.

In the bottom region, on the left, you'll see an area where you can select the thing you wish to change the key command or create one. You'll see that there is no Workspace names here, only by their order of appearance; hence the need to make sure the order is the one you want. 

You will see that the basic intended key commands are set to Fn keys. I do not like dealing with Fn keys, so I changed them to "Shift-Command-Option-1." To do this, I clicked on the default , and that highlights that command and displays an "x" adjacent to the command. If you click on the "x," you will delete the command. If this closes up, just click in the region, and you'll see the blue/black highlight, but it will be empty. Enter the key command you want and then proceed to any others. 

 Now, close the window and you're done.

Let me know if this works for you or not, or if you have any other questions.