Select 'Track Add' from the Linear Draft toolbar. Follow the prompts to select a structure.
Once a structure has been selected, select the left and right rails of the additional track.
When the right rail has been selected, the 'Edit Tracks' form will be displayed.
The additional track will be shown in the section 'Additional Tracks' in the lower half of the form. The track can be renamed by right clicking the additional track and choosing 'Rename'.
Close the form to confirm.