I am not sure how to ask the question so here is a picture of some idea that came to mind
So for example, when you run my "custom launcher" it displays a window with a couple buttons on the side which you can assign values to. When you click on a button, the appropriate program will run in the big panel on the right (in window mode).
This is all from the user's perspective of course. They will just see that the program they want to run appears in that panel. The actual implementation may have nothing to do with "one program running inside another program"
My own use case is limited to windows desktop platforms only, but if it is possible to generalize it that would be nice as well.
Is this actually possible? Can I write such a program that will run another program inside a panel? The program that's launched may be someone else's, such as MS paint or calculator.