The 3D Surface Note Measurement provides functionality to specify the exact coordinates 

To Specify Coordinates for a 3D Surface Note

  1. In Settings > 3D Viewer settings, enable Show Measurement Information Panel.
  2. Open your native 3D CAD file.
  3. Select 3D Surface Note from the 3D toolbar.
  4. In the 3D Surface Note Measurement dialog window, fill in coordinates to place pick the surface point based on the selected coordinate system.
  5. Click Create.
  6. Click to place the note.
  7. Enter note text with the Enter key to complete.

Note: It is possible to enter coordinates placing the note marker off any surfaces.