Hmm, maybe either you or me misunderstood what moderator panel delivers: As far as I understand it it bundles
existing moderator functions for the most part, some of which are normally burried in acp. It does not or barely add new ones. There is no chat function in XF, so there is none to be expected in moderator panel.
I clearly understand the need for information exchange between staff and also understand, that the DM system is not optimal for that, even with things like Conversation Folders.
But then you could simply create a forum node with limited access for staff only. Pretty easy to keep the overview here. However, chat ist in opposite to that real time messaging - fast and typically history is not relevant. If you have the need for something like that continuously you must run a big forum with loads of staff that is on the forum permanently during work hours. But then: There are dozens of chat systems that have chat as their main purpose - they are thus by nature far better than a XF add on could ever be. Slack, Rocket Chat, Matrix, to name just a few. Free, freemium or comercially - whatever you prefer. There are also add ons that integrate such systems into XF as well as dedicated chat systems for XF:
xenforo.com
Feature-rich, mobile-friendly chat application with Rooms, Private Conversations and more.
A lightweight shoutbox widget with active user list, staff room, archive and "real-time" mode.
K
Adds live forum conversations using websockets
K
Integration with scalable real-time messaging server.
As you have not made clear what the problem ist that you want to solve but rather requested a concrete solution directly it is hard to tell what can suit your needs. What's easy to tell is that your request seems not to target moderator panel and that there are many solutions available for it.