Setting channel as main chat

[defnad]

I think it's been done before but I can't find any threads or addons. I'm talking about how if you use the /guild or /g or /party or /p chatting, then that channel becomes your main active. If you hit Enter, it will come up. There is a part of Cosmos, a reply manager, that made an extra window that only showed your replies and if you hit Enter while in that window, the Reply would come up.

How can I make this happen for any specific channel, say a channel I've created (/join RandomChannel)? Then if I open that channel in a window, it will be my default chat.

Thanks for any help.