Normally I‘d say just like you would change views when flying „normally“ (not replay). But since you‘re asking I guess that doesn‘t work for you? How exactly are you trying to switch to external views, via keyboard shortcuts?
When in doubt perhaps try the Camera menu in the toolbar in MSFS?
UPDATE: Since I just saw that you replied to someone else below just now (on purpose or accidentally): I am the author of Sky Dolly. So which application are we talking about here exactly, to begin with? 