Hi Shachar Tzin! That yellow icon is there to warn you: Skins - Spine User Guide: Skin bones
If a bone/attachment/constraint not in a skin is parented to a skin bone, the bone may only be active when the skin bone is active, causing a warning icon to display next to the bone name in the hierarchy.
The mesh will look messed up because suddenly the vertices that were bound to a bone have the bone missing, but just add the bone in the correct skin to restore it.
