Hi,
Yes you can do this by changing the display layout in Display Settings.
In the above example, display #1 is the notebook monitor and display #2 is the external monitor
To set extend to left, select display #2 and drag it to the left of display #1
To set extend to right, select display #2 and drag it to the right of display #1
To set extend above, select display #2 and drag it above display #1
To set extend below, select display #2 and drag it below display #1
Thanks,
James