I believe you can get it to show a tooltip explanation of each of the context menu items by holding the ? key while hovering the mouse cursor over them. They probably don't all have tooltips, though.
My copy is currently broken while I rejigger the windowing system, but I think these are all the options in the special-move menu:
Set DestinationMakes the next left-click on space set the destination of the proposed move order (sets the location of the "X").
Group MoveIf toggled on, makes the proposed move use group-move logic (like what you get with G+right-click).
Formation MoveIf toggled on, makes the proposed move use formation-move logic (like what you get with J+right-click).
Then there's a "spinner" toggle that has three states you can change between by left-clicking it (I think right-click toggles it in the other direction, but I forget) :
Fire While Moving - no modifier, normal stance.
Stop To Engage (Attack Move) - makes the proposed move use attack-move logic (like what you get with X+right-click).
Chase Enemies (Free Roaming Defender) - makes the proposed move use free-roaming-defender logic (like what you get with V+right-click).
Queued MoveIf toggled on, queues the order on to the end of the existing command lists (like what you get with shift-right-click).
ExecuteActually issues the proposed move order.
(just quoting the tooltip for the next two)
Catch Right Clicks"Will treat right clicks outside the context menu as if setting the destination point and issuing the order immediately.
This can be very useful if you want to set up a complex movement order type and issue several queued commands without holding down several keys the entire time."
Remember Modes"Normally when you open the Special Move menu it sets its Group, Formation, and Stance toggles from the state current selection.
If "Remember Modes" is on, these toggles will stay on whatever settings you left them on (until you exit the program). This can be useful when giving the same types of complex move orders to distinct groups."
BackGoes back to the top-level have-ships-selected context menu.
Let me know if something doesn't make sense