If you're an in-house Pro, you can have unlimited queued jobs from your network. If you're not part of an in-house network, you can only have 1 queued job.

If you're working on an active job and receive a new request in your wheelhouse, you can accept the job by tapping Queue Job, and it'll automatically get added to your job list. The same happens if a work order is assigned to you. When you finish your active job, you'll be taken to your queued job list. Under Jobs, you'll also find your open and available requests.