This might well be the dumbest question you've ever been asked regarding help and support but I just picked up construct yesterday so you can probably forgive me not being too well versed in the ins and outs.
I've found that while trying to use the built in sprite editing program, using the resize canvas tool does not adjust the central point of the image and I can't find a way to move this. If I build the sprite in the default size and then use the Common tab in the properties to adjust the size then this resizes it AND adjusts the central point but this is not ideal if I wanted to use the built in sprite editor for anything more complex than square boxes which is what I was fiddling around with just now.
Am I missing something completely obvious in adjusting the central point of a sprite or is it not possible when using the image editor?
Another cool trick for hotspot relocating is to use the numpad on your keyboard. "5" places it in the middle, "4" to the left, "9" to the upper-right, you get the idea. It's a lot easier and faster than placing the hotspot by hand.