rocketpoop If you would like to reuse the mesh vertices and weights to another mesh in the same slot, you can use linked meshes: http://esotericsoftware.com/spine-meshes#Linked-meshes
Also, vertex positions can be pasted to a different attachment, as long as the same number of vertices is selected: http://esotericsoftware.com/spine-tools#Vertex-positions
If you want to reuse the weight settings, not only the vertex positions, you need to duplicate the original mesh attachment and replace the image path of the duplicated attachment.
An issue ticket for adding a way to copy mesh configurations to another attachment directly is on our roadmap: EsotericSoftware/spine-editor#551
Also, we have another idea that allowing linked meshes to be moved to a different slot: EsotericSoftware/spine-editor#195
You can subscribe to the issue tickets, then you will receive additional notifications upon any progress.