https://github.com/5argon/SpineTimeline
I have immediate need to animate my SkeletonGraphic
and couldn't wait for the official one, so over the past week I made some custom tracks that could animate it and I thought someone may need it.
A per-track AnimationState is cleared out and remade on every evaluation, that may make it not as efficient but in exchange allow deterministic timeline scrubbing in edit mode. During the duration the original AnimationState is frozen and the timeline try to keep it from taking effect.
The clip could use all extrapolation modes, speed modifier, and looping. Unlike the official it is not going to be backward compatible with 2018.3/4, but you could use markers to flip and set animations. In the gif, unlike the official timeline implementation each clip is a sampled state and not a command, thus when timeline ended it would reset to setup pose. The marker at the final frame instead take this task and make the skeleton continue an animation after the timeline. Enjoy.