Comment # 1 on bug 1093071 from Stefan Hundhammer

The YaST Qt UI does a QWidget::raise() for each new dialog (created from the
Ruby/ex-YCP application code:

https://github.com/libyui/libyui-qt/blob/master/src/YQDialog.cc#L186

We are doing that for a good reason because every so often it happened that
some weird window manager got the window stacking wrong and a small popup
dialog would end up behind (!) the main dialog, rendering the entire YaST
application unusable. Only very advanced users try [Alt][Tab] to check if maybe
some modal popup is hiding behind the main window; to the great majority of
users, that application has become unusable.

This was a workaround for an even larger number of other bugs that turned out
to be complete showstoppers for many users. We never liked that approach, but
it was a feasible workaround for a real-world problem.

What you are asking for, however, is a minor annoyance that affects only a very
small number of users, mostly in our internal QA department.

For more details, see also 

  https://bugzilla.suse.com/show_bug.cgi?id=246934#c23

We will definitely not go back to make the YaST UI unusable for average users
in many cases when some window manager misbehaves (which a surprising number of
them tends to do).

If anybody is actually willing to spend time on this and has a solution that
does not break things (i.e. go back to hiding small popup windows behind the
main window in some cases), we will seriously consider it. But so far, nobody
seems to have a bright idea what can be done.