This is more of a how-to-use-the-interface question. I am a nomad and have just won subjugation of Arabian empire. For some (to me unfathomable) reason, all vassals of the previous ruler become my vassals. Since clan leaders don't get upset about revoking titles, I want to revoke every single title in the Arabian empire (including baronies, mosques and cities). That sounds like a lot of clicking though. Is there any way to do this quickly?
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Choose your Casus Belli wisely. You must have chosen a casus belli which retains the vassals of enemy in case of your victory. I have the horselord DLC but I haven't yet played it (Just had a test run, didn't quite like it). Anyways, to answer your question, no you can't just do that.
You either have to manually revoke all the titles. Or you could write a custom event which would be triggered as a result of a successful invasion to revoke titles of all vassals which are not from your culture group (Which would be your newly conquered vassals, to be precise but I am not sure if it is possible to revoke ALL titles held by a vassal. Event could work for primary title at least). But that would be modding. In original game, nopes, you can't.