Does one of these tools support an animation timeline with arbitrary seeking? Essentially I want to be able to have a progress slider representing the current time, and if the user clicks on any time on the slider, all animations should spring to that state, like a YouTube video. I played around with GSAP, anime and some others, but none properly supported playing the animations "backwards" (while jumping back).

I wrote my own implementation of a declarative animation engine (i.e. the same timeline position always looks the same), but I'm pretty sure there are still a couple of bugs allowing you to go out of sync.

Has anyone done any benchmarks comparing the different solutions?

I hit a performance bug with greensock once and just quickly wrote my own simple animation framework, which I am using ever since, but I suppose it can be done better. I would think the native browser animation capability is superior?

I was looking for an animation library some time ago, and theatrejs looks incredible. Anybody has any experience with it? In the end I used blender for what I needed, but I got very curious about it.

I used motion.dev on a couple of test projects when I heard of it. And it's nice, the docs can be a bit lacking, though, and the userbase is tiny enough to have little to no discussion online.

any good comparison table between them?

GreenSuck is not free.