Selection of a Layout for a page/tab widget in a QToolBox or QTabWidget is near or just impossible

Object Inspector Context Menu

This context menu does not show the layout selection option for the selected page or tab widgets in a QToolBox or QTabWidget. ()

The children of the tab/page do have the layout option but it changes the parent.

Work-around

I open the ui-file in an editor wrap the child widget(s) with <layout><item> tags and reopen it in the designer.