XF 1.4 Allow replies inside subforum but not threads to be created?


Well-known member
Is it possible to have a forum where threads may be created and then moved into a subforum in which the subforum threads cannot be created but replies may be posted in this existing subforum?

Hierarchy looks like this:
Promotion Vault
--Webmaster sites

Threads can be posted/started inside of Promotion Vault but not Webmaster sites, but replies can be made to threads moved to that forum.

Is this possible with Xenforo? If so, how can it be done?