In this tutorial I will show you how to make a 2nd Viewport in this cool Source Filmmaker program.. And so for this, follow the instructions. ( yes i can't take screenshots due to windows problems , so you only have to take pictures from your phone in terrible quality , my apologies )
Launching Source FilmMaker
Here it starts , and how to make this rectangle from the bottom left?
find the Windows tab on the top left and put it on it
after we find the section there “Secondary Viewport” push
after clicking , such a window appears
Clamp the tab above this window “Secondary Viewport” and drag it wherever convenient
Done! it's very simple , now you have 2 “monitor” or even more