How is it determined which files in the job queue will be processed first?
The jobs will be arranged in the queue according to their creation time and priority.
The jobs with higher priority will be placed in the queue higher. If all jobs have the same priority, they will be placed according to their creation time (older jobs will be processed first).
If some jobs are already in processing and there are no free cores, the processing will need to finish before the next job can start being processed (even if it has higher priority).
Priority setting is available in Workflow Properties. Job's priority can also be changed in the Jobs pane for jobs that are already waiting by right-clicking the jobs and changing the priority in the context menu.