In full screen you can use the following key-combinations of [Ctrl]-key together with a numeric key of the
numeric key-pad:
[Ctrl]/[2] : Free resize down
[Ctrl]/[8] : Free resize up
[Ctrl]/[4] : Free resize left
[Ctrl]/[6] : Free resize right
(of course unless you've redefined the default key definitions for this under
(rightclick >) Options > Preferences > Key definitions & WinLIRC *)
In combination with using the same numeric keys without [Ctrl] to just move the screen and perhaps also using i.a. pan-in/out ([+]/[-] on numeric key-board) and/or zoom-in/out ([Ctrl]/[Up] - [Ctrl]/[Down]) you can accomplish almost anything; just experiment a bit with all these different possibilities.
(*: Note there can be separate keydefinitions for Windowed mode and Full screen mode)