How to add custom fields/validations on tasks?

We are onboarding to Zendesk sell and one of our use case is to assign multiple tasks with different priority and task type to our sales team.

The task option in Zendesk sell seems very vanilla. I would want to atleast add a validation (What the type is about) and the priority of the task (How severe or important the task is).

Is there any way to achieve this?