Something I found by mistake....
Have another app open like Safari.
Have a metro window like the mixer open.
Open a dialog box like tempo and with it remaining open, click onto the safari window.
Then click on metro's mixer window.
The dialog box for tempo is not on top as I might have expected.
You have gone to the mixer window.
Clicking the tempo dialog box (in its window) doesn't bring it to the front either. Clicking the dialog boxes title header does bring it to the front.
If you go onto a safari page and click back to the open popup it works fine. Even clicking onto the graphic editor window works to.
Is the mixer window different?
6.3.8.4
afterthought - is this to do with the fact you can adjust faders without bringing the mixer window to the front?