This is the trick: when you right-click a 3D view, the Save to New File option is grayed out, but when you put it on a sheet - its back!
Here's how to do it:
- Create a Sheet and place a 3D view on it. The 3D view has to 'contain' all of the elements you want to keep in the new file.
- In the Project Browser, right-click on the created sheet and select "Save to New File ..." (it will take a while as it collects the elements, then it will prompt you to save the RVT file somewhere)
- Open the exported file and Transfer Project Standards for Line Weights / Patterns / Styles and also Object Styles (and anything else you want)
Things that are removed:
- Design Options
- Floor Plans - well actually, the only view that remains is the 'export' view and the Default 3D view
- Everything else that was unused or not visible
- Floor levels
- The 3D Revit elements that you could 'see'
- RVT links if they were visible in the 3D view
- the Sheet that was exported
- Line Weights / Patterns / Styles
- Object Styles
For my test case, I also turned off all Annotation Categories in the original 3D view, and I scaled it so it would fit the sheet.
This workflow and the basic steps were from: