even I save the layout by pressing File/Save or File/Save As. I also tried CELayoutEditor 0.6.2, but still doesn't work
I thought it is a bug of the editor until I also see a post here
So it seems GroupBox doesn't have
parent/child relation with the controls which appear to be inside it
If it comes to that, in my opinion, CELayoutEditor should really forbid adding child to a GroupBox to avoid false apperarance,
because in the CELayoutEditor's "Brouse layout" window it appears that the GroupBox has a child which is actually not how it works.
So, I have to add a widget in the same level as GroupBox, and then move it into the GroupBox.