Aside from the fact that Win10 can launch and display multiple apps (A fact you most likely know but "ignore") the system is NOT restricted to them. If you want full scale applications - just start them. As many as memory allows / make sense on the screen(s) and desktop(s) (Jup, W10 can do THAT as well). And since the Surface/x86 all have a proper inductive stylus and well working handwriting recognition - they even work if you use the detached tablet (And have done so since XP Tablet Edition in 2003/4). Again it is safe to assume you just "forgot" that as well.