hotkey for in-game overlay pinned chats

So a feature I've found recently is missing one small detail to make it perfect.

The feature in question is the ability to pin a chat to the overlay to be visible in game. This is great for seeing when you get a new message without needing to tab out of the game. and you can reply by opening the overlay.

However, that's the slight issue. You HAVE to open the overlay to reply. I would like a mappable hotkey that allows typing in the pinned chat without needing to open the overlay.

something to the effect of being in a voice call with a friend playing a co-op game. this friend is not mic'd up and is communicating through text, but there is no in game chat so we're using discord. But they have to tab out (or open the overlay to reply to anything im saying with my voice. If there was a hotkey (that presumably would be mapped to something that doesnt interfere with the game, they could press it, the games controls would give way to the chat function as if the overlay was open, immediately (without having to click on it) type their message and then hit enter and it would send the message and revert back to the game's controls.