By using the Define option, the 2d sketcher mode will be activated. For auxiliary defined by extrusion, the tag tool will search for a closed boundary like lining parts tag tool. For auxiliary defined by point, the user will draw a circle that will be tagged with the appropriate tool and it will be used for the creation of a path for auxiliary's objects placed as external cells.

Once the user saves his changes, in the GUI each element will be listed with the name specified in the tag tool and corresponding cross-sectional area.

For cell type auxiliaries, user can create the geometry in external files that can be stored in Auxiliaries folder and then place those objects in the design file.

The default path for storing the external files is C:\ProgramData\Bentley\OpenTunnel Designer 2023.00\Configuration\Organization-Civil\_Tunnel Default Standards - Metric(Imperial)\OpenTunnel Designer\Cell\Auxiliaries.