These are support pieces, not standalone stations. If the benches and workstations are already specified, this is where you fill in the parts that make a full shift easier to work. Adjustable footrests come with a 12 inch or a 20 inch platform and move to fit the operator instead of the other way around. Back support cushions work in a forklift seat or an office chair, so the same piece covers a lift driver and a desk in the shipping office.
The pack carrying belt covers the part of the job that happens away from the bench, when someone is moving product by hand rather than standing at a station.
Spec these the way you would spec any other part of the station: by the person and the task. A packer standing at a bench all day and a lift operator running a full route need different support.