Who may run what: crews, their pace and their priorities
Not every operator may run every machine: only certified welders weld, only trained staff run the press, while anyone may fit, pack or check.
Built in A field or setting does it directly.
How
Use a shared operator pool (Project settings → Operators → Shared operator pool) and give it Crews, each with its size: welders: 1; fitters: 1 (resources.human_operator.crews: [{ "name": "welders", "count": 1 }, ...]; their sizes replace the pool size). On each machine only some crews may run, set Operated by (Hardware; "operator_crews": "welders", or "welders, fitters" for either). A machine that names no crew takes anyone. A job waits for a free operator of a crew its machine takes; jobs for different crews do not queue behind each other.
A crew may also work at its own pace and leave its own scrap: trainees: 1, 70%, 2% scrap ("speed_pct": 70, "scrap_pct": 2). A job worked by it takes its time divided by the pace (the mean pace when several work it), and each of its operators scraps that share of the units it works on, drawn as the step finishes (replaced like any scrap). A pace holds for the whole job; on a machine whose operator is needed only at the start and the end (machine tending) the pace does not apply.
Operators take next (Project settings → Operators; operator_priority) says which waiting job a free operator takes: first come (the default), the highest order priority (a hot order, Factory data → Priority), or the station with the longest queue.
The results list each operator with its crew (operator pool → by operator). A machine no crew of the pool may run is reported (OPERATOR_CREW_MISSING) and nothing passes it.
Check
Two operators for three benches, a frame every 170 s, 100 s at each bench. Free to go anywhere they keep up without waiting: 421 frames in 20 h, a lead time of 5.5 min. With one welder and one fitter, and only the welder allowed at the welding cell, they still make 420 frames, but frames wait 9.7 h in all for an operator and the lead time grows to 8.5 min: the welder is fitting or checking when a frame reaches the cell.
A trainee at 50% pace and 10% scrap beside an expert takes 200 s for a 100 s job, and scraps about a tenth of what it assembles. One operator for three presses, 83% busy: first come, a hot order waits 102 s on average (50 s of it work); with order priority 75 s.