Parameters of the Invoice & Billing system are in your Backoffice -> Settings -> Parameters -> Invoicing
1. Add a new param.
2. Column of defined params.
3. Customer column. It is possible to define params per customer. Note: If there is no customer defined, than this parameter is active for all customers.
4. Description of this param.
5. Content of this param
6. Delete this param. Note: It's better to rename a param (as old), than deleting it. Deleting really means that you will loose this functionality. Note: Some parameters are modelCarrier parameters. A kind parent parameter unable to remove, but able to modify.