Hidden Order Ids:
851971 (smart): This is a point or object targeted order that is like a right click.
852000 (skillmenu): This is an order with no target that opens the skill menu of heroes. If it is issued for a normal unit with triggers it will black out the command card for this unit, the command card will revert to normal after reselecting the unit.
851994 (buildmenu): This is an order with no target that opens up the build menu of a unit that can build structures.
852002 to 852007 (moveslot): These are item targeted orders that move the target item to a certain inventory slot of the ordered hero. The id 852002 will move it to slot 1, the id 852003 will move it to slot 2 and so on.
852008 to 852013 (useslot): These are orders that will make the ordered hero use the item in a certain inventory slot. If it's an order with no target or object or point targeted depends on the type of item. The id 852008 will use the item in slot 1, the id 852009 will use the item in slot 2 and so on.
851976 (cancel): This is an order with no target that is like a click on a cancel button. We used to be able to catch cancel clicks with this id back then but this id doesn't seem to work any more.
851973 (stunned): This order is issued to units that get stunned by a spell, for example War Stomp (AOws). This is probably a hold position + hold fire order. The ordered unit will be unable to move and attack.