1. It is required to add the structure name to 3D view area. Label should be shown at top-left corner of 3D view area for every structure.
2. When many structures are opened in the 3D Structure View, then each 3D view should have Close button at top-right corner.
3. When many structures are opened in 3D Structure View, then 3D view should not have Close button at top-right corner.
4. Icon for Close button is the same as Close button of DotPlot.

For more info see here.