You can submit as many requests as you need. Your designer will work on them in order of arrival unless you've set a higher priority to a specific design request.
If you need an urgent request to jump up your design queue, just let your design team know (or change the priority to "Urgent") and they'll pause whatever they're working on for you and start working on that task. After that, they'll continue working on your other tasks.
It's all about the relationship between your designer and you. You can view all requests in the dashboard so you can prioritize them as you wish.
