The problem of this and related tickets is from how elements are grouped/ungrouped inside single child containers.

Right now we are creating the new parent, adding it to the single child container, and then moving the other elements inside the new parent. But the first operation is not possible because the container can only have 1 child at the same time. We need to find another way to implement this kind of operations.

Just noting that this issue might also be related to 0002836 (unsure though, because templates are weird sometimes).

The possible solution could be to create a group element in-memory, store the original content of a single child container into a smart Ptr<>, remove the single child container content, add the original content to the group element, set the group element as the content of the single child container.

Unsure though as maybe detaching from visual tree and reattaching it is going to cause some assert/crash to happen. Maybe the solution would then be to Helper::Clone() the original content and add it to the group element and then just replace the content of a single child container.