Ok this is weird.
If I type “window.Twitch.ext” on the popout’s console, it comes as undefined (actually an error, because window.Twitch itself is undefined).
But if whatever code I already have on my panel.js tries to access window.Twitch.ext, it works just fine.
Since I always try to check stuff on the console before using them on code, it seems this is me not understading the scope of variables or ‘where’ they’re actually stored. Regardless, my problem is solved. Since I DO can access the data (just not on the console itself), I can do whatever I want now.
Thanks for the reply, @BarryCarlyon !