1. You marked a specific task as private.
2. You set the permissions of that specific tasks board or tasks group to be hidden by default.
Hover over the task board or task group and then from options menu click on "permissions".
Select the person you would like to apply the permissions to.
Change permissions accordingly and that's it, the changes are then applied.
If you have hidden a task group from someone and then delegated one of the tasks inside that group, they will then be able to see only that task inside the group.
Published on: 06 / 02 / 2018