Hi, not sure if you have fixed your problem yet or not but to do windows capture on the mac you will need to go to "MacOS Screen Capture" and make sure you checkd the second box that reads "show fullscreen/hidden windows/applications"
if you don't check that box then you will see that your window list is very short and doesn't show all of your applications like this
But, if you check "show fullscreen/hidden windows/applications" box then you click on the window dropdown list you will see there are a lot more of options then you could click on your browser like this image down below
Hope this help people that want to do window capture on the Mac but don't know how to!