We are sorry for the inconvenience. Indeed some (non-crucial) features have been removed by Pharan some time ago, and we did not yet have the time to re-activate the full feature set again (see this issue ticket).

I have now updated the documentation md file to reflect the current state. It will be included in the next unitypackages.

Is it possible to know when it will be back ?

Yes, you can subscribe to the issue ticket above, this will notify you upon completion of the task.

If you meant an ETA, I'm sorry that I cannot provide you with one. Unfortunately many important tasks are in the queue before this one, so I fear it will not be until the following months when it will be completed.

Hello,

Giving the new Spine version is out, can we expect that less important feature like this one are going to be fixed ?

Thanks

You can always review the Spine roadmap here:
Spine Roadmap

Please note that bugs receive the highest priority, followed by enhancements that are enabling compatibility with crucial Unity features (such as Lightweight Render Pipeline support in the past and 2D Lighting support yet to be implemented).

Ok. But I found weird that we are not able to use Spine with the main Unity animation tool (Timeline) and that is not a priority to fix that. Timeline was here for a long time now, way before SRP and 2D lightening and its utility from an animation point of view is way much important of those later. Is great to have Spine compatible with Unity but is really important to not just be "runtime" compatible but to improved the workflow and the tool compatibility.

Thx.

Honestly, timeline support would be a game changer.
Didn't realize I needed until just now. Ran into a timing issue that would be so easily solved with timeline.

Edit:
Figured out a workaround using Unity 2019's new Signal Emitter and Receiver with timeline.

You just need to add a Signal Emitter to your timeline, then add the SignalReceiver script to the object you need to react to the emitter. Then call the function you want to run from the SignalReceiver reaction.

public void PlayKissAnimation() //called by Timeline Signal Receiver
    {
        skeletonAnimation.state.SetAnimation(1, Kiss, false);
        skeletonAnimation.state.AddAnimation(1, Blink, true, 0);
    }

I guess there are some misconceptions:
Timeline has always been supported, you can use Spine Animation State Track and Spine Skeleton Flip Track. What has been deactivated by Pharan some time ago and removed from the Timeline extensions was Spine Animation Track.

Timeline support is available here for download as a separate UPM package:
"Timeline Extensions UPM package" com.esotericsoftware.spine.timeline
Spine Unity Download: Download

The issue ticket above deals with a clean reimplementation which shall cover all required aspects, such as setting playback speed and other things.
We are sorry for the trouble and misunderstanding.

Is there any support for Skeleton Graphics playback within timeline?

I have added a section to the spine-unity docs pages for further reference:
spine-unity Runtime Documentation: Timeline Extension UPM Package

Forum user Sargon has kindly shared his implementation for SkeletonGraphic on this forum thread:
Spine timeline plugin for 2019.1
Thanks again @Sargon!

The Spine timeline package has been updated, now providing the previously removed features and more.

See the documentation section here:
spine-unity Runtime Documentation: Timeline Extension UPM Package

From the changelog:

SpineAnimationStateClip now provides a Speed Multiplier, a start time offset parameter Clip In, support for blending successive animations by overlapping tracks. An additional Use Blend Duration parameter (defaults to true) allows for automatic synchronisation of MixDuration with the current overlap blend duration. An additional Spine preferences parameter Use Blend Duration has been added which can be disabled to default to the previous behaviour before this update.

You can download it here as usual:
Spine Unity Download: Download

We hope that now all previously provided Spine Timeline features have been re-activated and the additional features make it more comfortable to use: now you can finally drag your animations over each other to create transitions.

Official Timeline support for SkeletonGraphic and SkeletonMecanim is yet to come, but at least SkeletonGraphic is within reach - stay tuned for updates.