If you need multiple users to work on one Task, there are overall three ways to do it.
1, assignee and co-workers
you can set one person as an assignee, and the others as coworkers.
Co-workers get notifications and are able to manage the task just like the assignee.
there are two ways to add a co-worker
- you can add him while creating a task
- You can add him to an existing task
2, Group assignment
You can assign a task to a group, the group will receive notifications and can manage the task as one.
To be able to assign a task to a group, make sure, you have this option turned on in administration>>settings>>task tracking
Look for this checkbox on the right side.
You will then see a group in the assignee list ( the group has to be a member of the project, just like a regular user)
3, Distributed task
How to use distributed task and how to set it up can be found in this knowledge post