You can refer to this previous post, but unit labels are not available as an option in the Place Datagroup Annotation tool. It is controlled by a VBA , but the unit label is available when using the mechanical rules. The duct is labeled with units and MU labels in the drawing view. The Annotation Cell does not change at all even if the text is edited to include mm.
communities.bentley.com/.../239254
communities.bentley.com/.../239254
