Many third-party aircrafts have their own set of keys assigned to different panels.
For example on default aircrafts, pressing SHIFT-3 will invoke the GPS panel. But this key-combo is not necessarily able to call up the GPS panel on Carenado and Aerosoft aircrafts.
If one has assigned an external button, say button 3 on a Saitek FIP, for the GPS panel, the difference between the default and third-party aircraft panel key assignment therefore will be quite annoying when aircrafts are changed.
To standardize panel key assignments across different aircrafts:
Open the panel.cfg file under the Panel folder of the specific aircraft
Rearranging the order of Window definition as needed as illustrated below will do
Although this tweak generally applies to all third-party aircrafts, files and settings involved may be different from vendors to vendors.