This will set the clip label to "flip" which is better than showing full class name.

[CustomTimelineEditor(typeof(SpineSkeletonFlipClip))]
public class SpineSkeletonFlipClipEditor : ClipEditor
{
    public override void OnClipChanged(TimelineClip clip)
    {
        var flipClip = (SpineSkeletonFlipClip)clip.asset;
        if (flipClip != null)
        {
            // TODO: you can custom the label based on setting here.
            clip.displayName = "Flip";
        }
    }
}