Shortcut Key	Where Used	Function
Ctrl-S	RE	Saves your work - use it often (every five minutes or less.  Every 20-30 minutes, save your work and quit RE. Re-boot your computer and start again.
Y	RE	Aligns terrain with track by lifting or depressing terrain (ie terrain comes to track)
~	RE	Undoes the last terrain change
Ctrl ~	RE	Undoes all terrain changes since last save
H	RE	Places an object on the ground from above/below the ground (does not straighten a tilted object - see N )
N	RE	Straightens an object once you've misaligned it by tilting it (does not place it on the ground - see H )
V	RE	Punches a hole in your terrain (removes texture for a tunnel)
END	RE	When used with the cursor keys on the numeric pad (Num Lock OFF), you achieve much finer control for moving or rotating
0 (zero)	MSTS	Turns on Compass and latitude/longitude in the actual sim
Ctrl +	MSTS, RE	Shows bounding box for rolling stock and track objects
Ctrl ]	MSTS	Uncouples last vehicle in a consist
Shift-Z	MSTS, RE	Shows your frame-rate in bottom right corner of your screen

Codes used above

MSTS	The actual simulation
RE	Route Editor
AE	Activity Editor