Has anyone gotten inertialization going with their animation blueprints? Searching gave literally 0 results on the forums.
It looks great and I would like to implement it, but the inertialization node seems to be missing and I cannot add it to my blueprint. Does it have to be enabled somewhere?
Yes. After picking it as blend mode you must use INERTIALIZATION NODE somewhere in your graph AFTER the blends. so easiest is to place it as the last node just before final pose 
Inertialization isn’t an option in the list of blend nodes in my state machine. Hmm…
And is it possible to use inertialization for blendspace based animations?
If you are not seeing the options in the screenshots below, you probably need to update your engine to 4.24. (don’t remember if it was around in 4.23)
I don’t remember the stream, but there is one that covers this system. You can think of it like this: Whenever you get a transition/blend (state machine or blend poses) the transition happens instantly and only one sequence is playing at a time. However, your blend time tells the inertialization system for how long it should apply the velocities from the previous sequence. This means that if you are used to transition with time remaining at 0.25 seconds, it means 0.25 seconds will NOT play from your sequence. It will cut at that exact point. Therefore you must design your sequences in a way where you end at the right pose and movement for a good transition. If you don’t, you can get weird side effects like arms transitioning into the character’s body. The advantage is that you get more exact transitions from a gameplay perspective and don’t have to do additional math in your head to include transition times in your gameplay interactions.
Also note that you are free to have multiple inertialization points in your setup and can mix them with Standard Blends. Which means you can have one state machine that uses only inertialization, but have other blend nodes that don’t use it. (also note that inertialization in a state machine is per transition, it is not global to the state machine)
There have been a few moments in the last few weeks where inertialization has helped me tremendously. Some animations have been simplified, because I don’t need to include a transition zone at the beginning/end. Inertialization has also helped with multiple state transitions. Sometimes you can’t design an animation to work with every scenario, which means you either have to create multiple transition animations or live with abrupt changes. Intertialization seems to give a sweetspot in some complex graphs and “just work”, but to get there you kinda need to experiment with it.
I recommend NOT trying to master it in one go. Just replace parts of your graph as you go along, it will give you time to understand it intuitively.
Aha, it appears it was added after 4.23 then, I only have custom and standard as options. I guess it’s another thing to keep in mind for if I want to update my project at some point.
Just to share of what I’ve learned after using inertialization:
Just like montages.Basically my idea was - slam one of those nodes at the end of the graph and it will work 
and after 2 days of debugging what causes bad ik and anim frame skipping… I realized there is no frame skipping, only IK and additive gives weird high velocities that ends up in terrible blends.
