I've created an issue:
EsotericSoftware/spine-editor770

The reason Spine only detects the visible images is because it doesn't know the others have changed size. To know that, it would have to load every image. There could be thousands, so that's not something it can do periodically just to check. We'll need to provide a button to scan all the image sizes.

Maybe the best available solution at the moment is to make each skin visible and answer the popup. use hotkeys where possible, eg Next Skin. I apologize this may still be tedious. It may be easy to miss a mesh that is only visible in an animation.

To see if Keep size and Stretch are working correctly, look at the images in edit mesh mode with Deformed unchecked. We'll also check it's functionality.

raaan127 I have confirmed that I can reproduce the problem you describe with Spine 4.1.24. I have tried several things, such as enabling "Show all skin attachments" in the view settings of the Tree view and pinning all skins in the Skins view, but I have not been able to successfully replace all attachments with images with added padding. Unfortunately, I cannot think of an effective solution. It may be effective to export your skeleton once in JSON format and then edit the JSON file, but I can't be sure. Please give us some time to see if other members of the Spine team can provide you with better solutions.

@raaan127 You need to add a SortingGroup component at the SkeletonRenderer's GameObject. Unfortunately the MeshRenderer API does not allow to customize the sorting point from center to pivot, therefore this additional component is required.

You can find older forum threads about this topic here:
https://esotericsoftware.com/forum/d/10783-sprite-sort-point-for-spine/4
https://esotericsoftware.com/forum/d/13990-modify-skel-parts-renderer-to-sort-using-a-quotsorting-groupquot

You have resurrected a very old thread which is by now obsolete.

You can use the SpineAnimation attribute now, so the much more elegant way is as follows:

using UnityEngine;
using Spine.Unity;

public class AnimNameInspector : MonoBehaviour {

   [SpineAnimation]
   public string listOfAllAnimations;

   public SkeletonAnimation otherSkeletonData;
   [SpineAnimation(dataField: "otherSkeletonData")]
   public string otherSkeletonsAnimations; // dropdown list will be populated with otherSkeletonData's animations.
}

Note that the SpineAnimation attribute has some more useful entries apart from the dataField:
spine-runtimes/SpineAttributes.cs at 3.7