Parametric Design implicitly creates a new parameter whenever you Assign one of the following constraint-types and supply an unused parameter name (string) when prompted to do so by the software:

The name you give must conform to the naming rules given in the Assigning Parameters, section and must not be the same as an existing parameter name. If you give an existing parameter name, that parameter will simply be assigned to the constraint and no new parameter will be created.

When you create a new parameter with this procedure, Parametric Design implicitly creates a default definition for the parameter and then binds it to the constraint you're assigning.

By default, the new parameter is given the current value of the constraint. For example, if you assign a size constraint to a 10 cm line and give the label 'Len_3' at the prompt, Parametric Design will create a new parameter, Len_3, and give it a value of 100, assuming your current length units are mm. Note that parameters always use the units they were created with. Len_3, for example, will always be in mm even if you change your length units to inches.