I have since learned an even easier way to get back into the cockpit. The showcase view toggle method is not reliable because some aircraft are not big enough to have a showcase view inside the aircraft.
There are two toggles: Cockpit/External View Mode: [END key on keyboard]; and Toggle Drone : [INSERT key on keyboard.] Once in the Drone mode, the Cockpit/External view does not get you back into the cockpit, it just toggles between the drone and external view. The INSERT key gets you out of drone view so you can get back into the cockpit by the Cockpit/External view toggle.
So, there are three views (Cockpit / External / Drone) to cycle through, and a single button only toggles between two of them. This is the problem. The solution is between two keys: END and INSERT.