I can't find a button, decision, option, anything. The event fired to turn my warband into a waaagh, but I haven't been able to do anything about it, and a few years later I get the failed waaagh event.
Waagh grants a special CB but it can only target sufficiently large enough realms, though the requirements will be loosened in the next patch.Bumping, hopefully not without reason.
I have the same problem as OP, no special CBs for having the waaagh nomad government. I´ve been trying to read through the vent files in vain. I crept up to border contact to Reikland, nothing.
I only have the ordinary border invasion for greenskins, no available targeted decisions or anything anywhere. Periodically I get the "you didn´t go, which I bypassed with the 1000 prestige malus.
Thanks!