@kido0617 I'm sorry to say that Z Position is only respected when using Mode Follow. Please note that a Bone in a skeleton has no Z-position, it is only represented in 2D space internally. In the resulting mesh, any attachment's Z position is defined via the Inspector property Advanced - Z Spacing combined with the current draw order.

It would also not be well-defined what should happen if you could change the Z position of all attachments at a given bone, since draw order dictates which attachments are drawn on top of other attachments. Moving their Z-position would not change that since usually skeleton shaders don't write to the depth-buffer on purpose. As a result you would get an attachment which is moved far-back but which still renders on top of other attachments that are in front of it in terms of Z-position.

Mentioning for sake of completeness:
Regarding following Z position, there has been a bug which is fixed on 4.2-beta but will not be fixed on 4.1 to not break existing projects:
EsotericSoftware/spine-runtimes2255
So on spine-unity 4.1, the Z Position property has no effect.

@kido0617 What do are you trying to achieve, which leads you to wanting to modify the Z-position of a bone or attachment?

kido0617 Harald will be unavailable until November 12th as he is on vacation. I'm sure he'll give you some advice when he gets back, so I hope you'll wait until then.

@kido0617 Sorry for the late reply, thanks for sharing the video.

Potentially the easiest way would be to split the skeleton mesh into multiple parts via a SkeletonRenderSeparator component, isolating each part that should be split off as a separate MeshRenderer GameObject. This would allow you to freely move parts around while still automatically sorting everything correctly.

@kido0617 Glad to hear it helped.
BTW: Your game looks (and also sounds) very cool!