Turn to Reference: Reference Dimensions - Editing

To turn a regular dimension into a reference dimension, invoke the Sketcher Dimension dialog and click the button. In addition, the following occur:

If a relation was defined for this dimension (when it was a regular dimension) then it will become obsolete (when the dimension turns to a reference dimension). The Dimension dialog will appear collapsed and the interaction and functionality will change accordingly.
If this dimension was marked as a Leading Dimension, then it will be defined as such no more. It will not be available in Leading Dimension table nor will it have a distinguished color.
If this dimension was part of a catalog table, then it will be removed from the table. However, when double-clicking a catalog feature in a catalog part, in addition to showing the primary dimensions, any reference dimensions are also shown.