Running multiple scenarios at the same time (assuming standalone controller) is not possible on THE SAME controller at THE SAME time.
From your description of the problem I assume you are looking for multiple scripts (groups) running in the same scenario - if so then the answer is YES.
In the controller you add more Groups (scripts are called groups in controller) and define the number of vusers or % of total vusers (depending on scenario type & controller version) for the group. I have not seen any limit on the number of groups/scenario. I've never needed more than 15 groups in a single scenario thou ..