From FSDeveloper Wiki
Generic Action Properties are integral, and applicable, to all action types, (except where noted).
Activate Waypoints Action provides one or more AI object with a new list of waypoints. Waypoints are essential for the movement of certain AI objects.
Adjust Payload Action is used to set, or add to, the weight on a payload station.
Attach Droppable Payload Action is used to change the payload that gets dropped when the user presses a key configured to drop the payload.
Attach Effect Action attaches a single special effect (such as smoke, fire, contrail etc.) to one or more objects.
Change Object Type Action changes the object the user is in. For example, it can be used to change from one type of aircraft to another.
Count Action will add the value of the Count property to the Counter value in the given list of triggers (which should all be Counter triggers). Counter triggers will fire when a certain specified count is reached.
Custom Action is used to enable communications between a mission and a SimConnect client application.
Dialog Action is used to add speech to be rendered over the audio system, and/or text to be displayed on the screen.
Failure Action is used to change the behavior of one of the aircraft's systems.
Goal Resolution Action is used to set whether goals have been completed or not.
Play Animation Action will initiate an animation sequence on one or more objects.
Play List Action will play the specified music items on the adventure music track. Individual play list items can be set to a random position within the play list.