I've found a solution! Well, sort of -- it's a workaround, but it solves the issue. It would be nicer if we could access the "hidden" shortcuts in DDM 2.0 (or that it wouldn't hijack quite as many shortcuts frequently used elsewhere), but this resolves the issue as well.
I just installed DDM (Dell Display Manager) 2.0 because I rebuilt Windows. It appears that I can't change the PIP shortcut key combination ALT-P to something else because it is hidden away by the software. That combination interferes with gaming shortcut keys that I use (I didn't have this problem before). Below is a capture from the DDM 2 documentation stating that "only relevant hotkeys in accordance with your screen configuration will be displayed.". I can't find that option to change anywhere in the software. How do I change shortcut key combinations that I cannot see? Maybe the software could not use shortcut key combinations if it is not going to allow me to change them? [IMAGE]  
AW2521HF, DDM 2.0, can't configure shortcut keys