How do you associate a length parameter to a dimension in a family?

To associate a length parameter to a dimension in a family within Revit, utilizing the label dropdown under the modify dimensions menu is the correct approach. This process involves selecting a dimension and then accessing the options available for that dimension. By choosing the label dropdown, you can effectively link the dimension to an existing length parameter or create a new one if needed. This association enables the dimension to control or reflect the value of that parameter, allowing for greater flexibility in the design and management of the family.

Other methods mentioned, such as using the dimension tool dropdown or assigning parameters through the properties panel, do not provide the necessary linkage to parameters in the same way. The parameter management tool, while useful for organizing and editing parameters more broadly, does not directly associate a dimension with a specific parameter during design. Thus, leveraging the label dropdown ensures that the dimension remains directly connected to the intended length parameter, facilitating accurate adjustments and updates as the design evolves.