AnimationMixer provides no API to organize animations in a chain so multiple animations are sequentially played. However, it’s not hard to build something similar on top of the existing API.
If you add an event listener for the finished event to your instance of AnimationMixer, you will automatically be notified when an AnimationAction has finished its playback. This is the exact point to start with the next animation.
When i start playing a new animation my blendshapes reset to 0. They are not keyed in the animation.
How do you know they aren’t keyed in the animation? That’s the only way I’d expect blendshapes to be affected, unless it’s something in your application’s code… Either way, you’ll have to provide more information here for us to know what’s going on.