Inside the Twitch Dashboard/Extensions config view, onAuthorized provides a JWT to indentify the user.
When you click the button to open a new tab to your big dashboard if you don’t pass anything over (like say the JWT as a query string var to decode), then you don’t know who they are as it’s like loading your website from scratch.
The optimal approach is to do an oAuth loop
So for example EmoteMeter you can use its website to configure - https://emotemeter.com/ or you can use it’s dashboard config view.
The website will require oAuth login so the website knows who you are
EliteTrack has a “report bug” feature where I pass the JWT up to the URL so I will use that to verify the user but only for reporting a bug no controls
So you can decide waht do you, for your described use case, you would want to be doing an oAuth loop to idneityf the user and start a session on your external dashboard