Keyboard Maestro allows you to automate things in almost any Mac app and assign it a shortcut. Even cooler is that when you assign the same shortcut to multiple macros Keyboard Maestro shows a head-up display with a list of all macros with this shortcut for you to choose from. Create e.g. a number of macros that all create a new document in DEVONthink of a certain type. Assign them all Command-N. When you now press Command-N you are presented with a list of document types.
Learn more about how you can use Keyboard Maestro for automating things in DEVONthink in our user forum.