Got it!!!!!! Took me the whole day because I was looking at completely irrelevant stuff for most of the time (I only made real progress these past 15 minutes after typing out why I give up, thank you rubber duck). It is just one missing line, diff below.
@Andevrs this patches an issue where the bone attachment 3d would not update its warning after a change in its target skeleton until the project was reloaded or the tree was updated. Now it updates the moment the user changes the external skeleton property. (sorry for tag, not sure how else to send in a patch)
diff --git a/scene/3d/bone_attachment_3d.cpp b/scene/3d/bone_attachment_3d.cpp
index 9a47befd1a..e97d6b65cd 100644
--- a/scene/3d/bone_attachment_3d.cpp
+++ b/scene/3d/bone_attachment_3d.cpp
@@ -62,6 +62,8 @@ bool BoneAttachment3D::_set(const StringName &p_path, const Variant &p_value) {
set_external_skeleton(p_value);
}
+ update_configuration_warnings();
+
return true;
}
