Open Images in Preview doesn't work in Automator (How to use Automator task to open screenshots in Preview automatically)
After playing with it a little bit I couldn't get the process to work as listed in your screenshot, either. Here's a flow which works - in fact, it took the screenshot below. Note that you need to set this up as a service in order to assign it a keyboard shortcut. (Create a new Automator workflow and select Service as the document type.) Otherwise, if you save it as an app, you have to run the app every time you want to take a screenshot.

Once you have saved your workflow as a service, go to System Preferences > Keyboard > Shortcuts and select Services on the left-hand side, then scroll down on the right to find your service and set a keyboard shortcut.