I have a exe and this exe runs in full-screen mode only (no close button, no expand button). I need to take notes while using the exe. But pressing alt+tab every time decreases my motivation. It will be great if I use half of the screen for the exe and other half for the notepad++.
This link (superuser.com) discusses possibilites of how to make a window appear always on top of all other windows on Windows 10, regardless of whether it is focused or not.
If your environment allows installing such programs, this might enable you to keep Notepad++ on top of that other full-screen application.