I think we can get this from [`chrome.system.display.getInfo()`](https://developer.chrome.com/docs/extensions/reference/api/system/display#method-getInfo) and then check which display `isPrimary` Then when creating the windows, use the left/top/width/height etc in the call to [`chrome.windows.create()`](https://developer.chrome.com/docs/extensions/reference/api/windows#method-create)