Can you please just say what rights you need, nowhere on the wiki discloses a right that allows you to create or delete sub-forums. The most I see is this description of a moderator and this does not proceed to answer my question at all and I am listed as forum administrator, not moderator in my tribe. As a matter of fact it appears that this example below is the only time sub-forums are mentioned in the entire wiki
Forum moderator Allows the player to moderate the tribe's internal forum. This right does not include the possibility to create or delete sub-forums.