Each task can have only one protocol. If you believe a certain task has two protocols, it probably makes sense to split this into two tasks – each having a separate protocol. Nevertheless, you can create and save as many protocols as you wish in the Protocols repository, where they can be available to other team members and uploaded to different tasks.
If you still want to upload multiple protocols to one task, you can create one protocol describing different protocol procedures, where each protocol step represents an individual protocol. You can also create checklists that can otherwise represent protocol steps.