Be able to drag the parent of a tree into one of its children

[klazoklazo]

Description

I'd like to be able to have the ability to drag the parent of a tree into one of its children, as demonstrated here with Tree Style Tab.

https://github.com/user-attachments/assets/3eb51235-58e5-46be-adbf-547bc2cf8668

I'd like to also say that this is slightly different from https://github.com/mbnuqw/sidebery/issues/511 because being able to move an entire tree at once outside of this exception is something I'd like to retain.