The easiest way to do this is with the Node Edit tool. You can find that tool in the very bottom menu (the Edit Single Entities collection of buttons) on the left. It should be the top left button that looks like a red dot on a line with arrows above and below it. Click that button, select the mountain terrain in your drawing where you want to stretch it/move it, and pull that node to where you want it. You may have to hit redraw to refresh after you do it. You can repeat the command to move other parts. The other buttons let you do things like add or delete a node, trim and break.