Well, like I said in an earlier post to someone else, I don't use FTL so I'm pretty much just guessing based on my understanding of how it all works, but let's see if I can't work it out.

The first thing I would check is to make sure that the key isn't already bound to something else in game.
You can also try defining Shift F

Code:
<ApplyTemplate FTL "Shift F" "Shift F">
But because you are already using Shift as a modifier in your FTL Template, that might not act as you expect for your slaves. So perhaps omitting the modifier from the slave argument will work as you expect

Code:
<ApplyTemplate FTL "Shift F" "F">
Or if you are looking for everyone to do something outside of the normal cast {everyone uses a modified spell on Shift F, such as Hearthing} you could define Shift F as a normal hotkey without the FTL

Code:
<Hotkey Shift F>
		<SendLabel w1, w2, w3>
			<Key Shift F>




I'm not sure what all the extra labels are for at the top.

Code:
//-----------------------------------------------------------
// DEFINE MAIL LABELS FOR SENDING KEY STROKES.
//-----------------------------------------------------------
<Label w1 Local SendWinM wow1>
<Label w2 Local SendWinM wow2>
<Label w3 Local SendWinM wow3>
<label win1 local SendWinM wow1>
<label win2 local SendWinM wow2>
<label win3 local SendWinM wow3>
<label mwin1 local SendWinS wow1>
<label mwin2 local SendWinS wow2>
<label mwin3 local SendWinS wow3>
<label current local SendFocusWin>
You aren't actually using any of those highlighted labels from what I can see.