Hi Petr, there's a list of the command names that you can put in for shortcut keys here:
http://moi3d.com/3.0/docs/moi_command_reference11.htm#shortcutkeys

So for example if you want to set up D for boolean difference, go to Options > Shortcut keys and push the "Add" button, a new entry will appear at the top of the list. In the left-hand "Key" column put in D and in the right-hand command column put in the name for the boolean difference command which is BooleanDifference , note no spaces in the command name.

- Michael