When using spine unity, I found a long-standing problem that has not been resolved. That is, it is impossible to preview each frame in the animation window. It's really inconvenient if you want to change a component on each frame of the animation.
I have read previous posts, all of them have the same result that the feature does not exist due to API limitations in unity.
After 2 days, I figured out how to do it smoothly as shown in the video above.
The version I use is 2017. Higher versions can certainly do it the same way, if not easier.
I have done preview animation spine in Animation Window
@locloz Sorry to hear it has been causing you troubles, glad to hear you've found a solution. The problem was never to integrate a skeleton preview with the Animation window, but to preview transitions of the Animator (Mecanim) window (the similar window name may have been confusing). That's also mentioned in the corresponding issue ticket here.
Nevertheless, we will integrate this feature that you showed above in the runtimes in the near future, so that users can at least benefit from this slight improvement, even though it won't cover Mecanim transitions.