The Create/Modify Legend Unit command part of the Documentation panel defines a set of elements that will be calculated into the legend unit.

Create / Modify Legend Unit command
Run the Create/Modify Legend Unit command and select all the elements that you want to include in the legend. Selection can also be performed before calling the function.
Make selections in the dialog box:
Select the category (multiple selection is allowed):

Select category
Select the parameters using the Filter option from new dialog and the Add or Remove buttons.
Note:
The parameters from the linked file can also be included in the parameters list by checking the specific box.

Selection of parameters
The values of the parameters can be overwritten by selecting the parameter and using Modify.

Edit parameter
After the changes are made, click OK.
Next, click on Selection of members for repeat and make a selection of elements.

Selection of elements for repeat
Choose the direction, type the distance and click OK. This creates a parameter field.

Direction and distance
To modify the legend category and parameters, add more parameters, change their order or change the array of parameters, just run the Create / Modify Legend option again and go to the step you need. Make the change and click OK.