The Job panel is where you can prioritize each settler’s tasks. By default, settlers will prioritize their jobs from left to right.
Using LMB and RMB, you can change job priorities so that a given settler will choose one job before another. Jobs set to the same priority level will be prioritized left to right. If the job box is empty, that a settler will never do that job.
Settlers will always do the highest priority job that they can find. If a specific job is not on anyone’s priority list, that job will never get done. The frame color of a job box indicates the settler’s skill level.
If a settler has a very low skill rating for a specific job, it is better to turn that job off completely for that settler – otherwise, there is a chance they will do the job and fail. This is important when it comes to things like harvesting. For example, a settler with a low botanical skill level could end up ruining the harvest, yielding no resources. So it’s best to let them focus on what they do best.