Maybe I'm just stupid but this seems like it should be really simple...

All I'm trying to do is put an existing object into a new vertical layout.
In right-click -> Layout all the options are greyed out, so I've instead just created a new vertical layout and want to plop the existing object into it... but there seems to be no way?

In the preview pane: The layout has no width when it has no objects, so I can't drag into it...
In the object pane: There is just no drag and drop functionality at all, which boggles my mind, since this would presumably be much easier that implementing it in the preview pane, and would be far more convenient as well.
Cut/Paste: Nope. It always just pastes as a child of MainWindow, regardless of the object I have selected.
In the property pane: No properties for parent or ancestor...
Nothing I can find in the right-click menus either...

So what am I missing? Every tutorial online just has people dragging and dropping in the preview but obviously that doesn't work when the object I'm dragging into has no width and REALLY should not be the only means of manipulation. I've been Googling for half an hour on this. Why is something so simple so seemingly impossible?