Ramon, that missing salesperson grouping is one of the sharper gaps once a couple of people start writing quotes. Right now Jobber won't let you pivot on a salesperson field, and the custom reports mirror that, so the piece you actually have to work inside is the JOBS list itself.
What usually covers it on the office side is a small custom field on jobs and quotes you label "Salesperson" or "Rep," set to the list type so each of your estimators shows up as a fixed choice. Once that field is on the records, the JOBS list filter opens it, and you can slice by whoever wrote or owns the quote — which also keeps the custom reports honest since they can pull on that field. Pair it with a saved/filtered view for each rep and you get the same day-to-day effect as the drop-down you described, without depending on a salesperson column the system can't expose.