![Avatar](https://secure.gravatar.com/avatar/6404ca1b046cd475b771f8236085522c?default=https%3A%2F%2Fassets.zendesk.com%2Fhc%2Fassets%2Fdefault_avatar.png&r=g)
You can add a related item to the task, but it will not work as a predecessor like in the work plan. However you might be able to create a validation rule that doesn't allow you to complete the task until the related items are completed.
Comment actions