A car on a ramp waiting for a part is not progress. The job card has to name the part, the supplier and the expected day, because that is precisely the answer the customer is ringing to hear.
Extra work needs an approval trail. A phone call agreeing to a second repair, recorded with the time and the figure, is the difference between an invoice that is paid and one that is disputed at the counter.
History belongs to the registration. What was replaced, when and at what mileage means the next diagnosis starts from knowledge, and it makes an honest recommendation possible rather than a guess.
Ramps are the constraint, not mechanics. Three bays and four technicians means the day is limited by space, and scheduling by ramp rather than by person is what stops a car being booked in with nowhere to put it.