Suggestion (Required)

While we already have a tag that allows for mobs to be persistent, there doesn't seem to be a tag that does the opposite.

I'm only suggesting this as while testing out the Alex's Caves mod, there's a certain mob that, despite being an animal that spawns "naturally", it cannot despawn whatsoever. Would be neat to have this sort of feature to further configure mob spawning.

Which mob is that?

The Atlatitan.

Their spawning mechanics are odd, and have specific requirements to even have them show up
(you need to defeat a boss to have them spawn, and they only spawn in an area where said boss is killed)

Seems like something about them makes them exempt from the regular animal spawning rule

Ok I made the mistake of playing version 8.1.1 while making this report, because in v8.2.0 this mob actually DOES despawn...

While I'm going to close this thread due to this, I still suggest having such a feature be added.
My apologies