Combines the selected meshes into a single polygon mesh. Many polygon editing operations can only be performed between two separate mesh shells once they have been combined into the same mesh.
Note: Use Mesh > Combine with the Construction History turned off so you can clear the history of multiple skinned items into a single cleanly-skinned mesh. (You can still use Mesh > Combine with Construction History turned on.)
Mesh > Combine > 
- Merge UV Sets
- Choose an option to set how your UV Sets should behave upon merging.
- No Merge
- Each UV set on each mesh becomes a new UV set in the output.
- Merge by Name
- Merges UV sets with the same name.
- Merge by UV Links
- Merges UV sets so that UV linking on the input meshes continues to work.
- Combine Skinning
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Binds skins, using the previous weights.