I believe there is no way of quick reply, it thats what your asking for. You need to target the player and enter text chat so communicate.
The comms system in ED sure needs alot of work if they want it to fill a purpose at all, in its current form it would have been better to leave it out altogether.
And ill keep on proposing a more general chatsystem like most online/mmo games use nowadays, completely optional, but that lets us who do wish to have some social interaction ingame have it.
Its a dead end trying to make contact in ED as is right now, and even tho its just beta so far, from what ive read the devs doesnt seem too keen on giving us a very social experience in ED.
One of the few big concerns i have with the game tbh.