Matika,
Sorry for the long pause between you posting and me replying, I did see it but I've been off sick with some neck pain probs for a while.
I don't like maximising the image as I feel like I loose control that way, what I do is reduce the image size and then pull the image borders out a bit so that the image sits in a grey area that isn't canvas - using the pick tool as you explained - I could then see the image's, or rather the layer's, corner handles etc.
I also noticed - being unfamiliar with PaintShop and thus trying things - that if you hold down the ctrl key when selecting a corner - you can then move that edge of the canvas to create (or remove) distortion like perspective distortion.
Depending on which way you move the cursor you can move either edge that the corner is a part of - neat!
I also noticed that rotation is also available but unlike PhotoShop, it's not at each corner but attached to the centre via that ... arm, coming from the central point.
Nice that rotation is easily avalable too.
Thanks very much for posting this.
FranOnTheEdge