The keyboard shortcut ctrl-option-p is supposed to invoke page preview (in wikitext editors from 2010 and earlier).
On my Mac, within VisualEditor (both visual and wikitext modes), it just types π instead. @Sadads reports that the equivalent command invokes preview on his computer system (with catastrophic consequences: T153937: LOST WORK BUG: If you use the shortcut keyboard command to preview, you lose all your changes.).
This keyboard shortcut should either work everywhere (ideally sans catastrophic consequences, but that's the other bug) or nowhere.