I was wondering the same thing. As far as I know, there is none : you have to create your tabbles, then organise them.
Then again, it’s still really painful when creating a lot of tabbles. There is no “tabble hierarchy manipulation” dedicated tool except for the Workspace, and there you only have access to the top-level ones, the nested ones being accessed through popups whithin which you can not select multiple tabbles at once to move them around.

Not being able to add directly a new child from a parent tabble, and not being able to easily change the nest-hierarchy of your tabbles is something that really infuriates.

But I guess it’s not something you have to go through everyday, so if it’s not currently available, while it’s being developped if it ever is, we can bear with it.