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.