Do you mean in the engine while the game is running? Resizing the window in the editor is trivial so I will skip that...
Yeah you can change the size of a window. Just set something like
Window.Width = 300;
Window.Height = 400;
with "Window" being a reference to the window that you want to change.
You can also scale the entities within a window. So for example if you have a window that contains an entity, which of course contains a sprite. You could do:
var entcontainer = Window.GetControl("entitycontainer"); //entitycontainer is the name of your entity object in the window
var entity = entcontainer.GetEntity(); //extracts entity out of the container
entity.Scalable = true; //Make sure your entity can be scaled, not necessary depending on entity def
entity.Scale = 50; //Scale entity to 50% of actual size
That's a rough guideline of how you could resize what's in the window. You should able to do what you want pretty much, I didn't try setting the entities sizes manually but you can give it a shot. Not sure if it works as I've never tried it and never needed too. You can try messing with the other window elements based on the small example above. Let me know if that helps at all.