To collaborate at the task level, you can add subscribers to tasks so that they receive notifications on updates or comments.

When you first add a team member to a task, they will gain access to that task if they didn't have access before, and will receive a notification telling them that you added them as a subscriber of that particular task.

If they stay subscribed to that task, they will then receive notifications for new task comments and when the task is complete.

You can add subscribers to a task or they can subscribe by themselves, so they stay informed and can participate:

Alternatively, you can @mention team members in a task comment, which will subscribe them to the task automatically. Learn more on @mentions.