You use workflow to add and edit workflow parameters in the workflow.

Choose the workflow name in the workflow panel.

Any existing workflow parameters are listed for the workflow.

Choose  + Add Parameter or select an existing parameter to edit.

The Edit parameter dialogue box is displayed.

The parameter name can be edited. 

You can also set the type of parameter from the dropdown menu.

The type of parameter will also determine the options for adding the value. A user parameter will expect one or more usernames as the value.

duration parameter will provide options to set the value using a specific period, a set date, a value reference or an ISO duration value.

Choose Apply to update the workflow in workflow builder.

Saving any changes to a bundled workflow will create a copy as a custom workflow. The bundled workflow will  change.

Choose Save and then Exit in the navigator panel to add to the space settings dashboard.