Spine is an animation system for games, so mostly uses whatever game engines and graphics APIs allow it to do.
This means it is subject to the same limitations that most game graphics have, and require some manual implementation where engines differ.
This unfortunately also means you mostly can't expect even the most basic compositing thing that "just works" in non-game systems like Photoshop and AfterEffects to also "just work" in Spine animations as you also wouldn't expect them to "just work" in Unity.
I certainly it was simple to do though. It would be cool for everyone.
But some amount of custom graphics programming is required even in Unity and it varies from setup to setup.
In short, no, you cannot do this in Spine editor at the moment.
You could probably do it in Unity but it's not specific to Spine. You could search the Unity forums on how to do it for MeshRenderers in general.
