There is no hotkey, because the minimap shows up automatically, if TCE detecting a stored planetary installation near your position. Not normally not required to look at the minimap, if you don't have a registered installation near.
You can hide the panel by clicking the HIDE button. To make it visible again, click the connect button, that was turned into a minimap button.
Thing is, i mostly use voice attack, and the map is distracting, so i hoped for a hotkey which i could translate into a VA command. An option to not automatically open would do, too.
Had a prob when i clicked hide, couldn't connect to EDMC at the next station bc the button didn't switch. After clicking on minimap again the Connect button wasn't there.