How to insert xul panel so doesn't minimize with window

问题

I create a panel and insert it into the id mainPopupSet area of the most recent navigator:browser window. I set the level to top so it shows over everything. But if that window closes the panel goes, also if that window minimizes it screws with the panel.

Is there anywhere I can insert it so it doesn't minmize? And will only disappear when Firefox exists?

来源：https://stackoverflow.com/questions/21926453/how-to-insert-xul-panel-so-doesnt-minimize-with-window