There’s a trick I found for LO3. Since it won’t let you drag a width/height marker over the edge of the page, you can drag another marker, so that the whole image enlarges and moves beyond the edge of the page. Once any marker is outside the page, you can drag it freely to resize. To me this is quicker than punching in numbers in the ribbon.
Although I’d still prefer to see “snap to edge of the page” instead of “edge of the page is an impenetrable wall when dragging”.