It depends on the airplane. I have done it a few times. If the panel is not too complex and you have another airplane that has something close to what you want and that's not much more than a pop-up, you can probably copy the GPS section of panel.cfg into the airplane you want it in. You will probably need to change the section sequence which will change the key stroke to activate it. It is complex to describe, not too hard to do once you get used to it. Panel.cfg is in the aircraft panel folder. It's a plain text file so Notepad is all you really need to make the changes. It will take some experimenting to get exactly what you want but that's part of the fun. Of course, make a safety copy for the inevitable "Boy, I wish I hadn't done that" situations.
I hope that sparks the desire - good luck and of course ask when you have something specific in mind.
Glenn