Is there a keyboard shortcut that moves Trello cards up or down in list order?
I want to prioritize cards without dragging and dropping.
Currently the feature you want is not implemented. The only way to prioritise cards without drag and drop is moving all cards out of the list and move card with the highest priority first back to the list.
I actually recently discovered Dynalist which allows me to hold the Ctrl button and arrow keys to move the priority. Highly recommended!