I don't understand what you're asking. What makes you think you have any control over how the browser uses threads?
In any case, if you just want to open a new window, obviously that's done client-side. As such, you'll need to find the appropriate JavaScript (or whatever you're writing on the frontend) function to do it.
In any case, if you just want to open a new window, obviously that's done client-side. As such, you'll need to find the appropriate JavaScript (or whatever you're writing on the frontend) function to do it.