You can set default assignees when editing a project card.
Then, when creating a new task in a project, Planfix will suggest adding these assignees to the task. The task creator will be able to agree to the list of assignees or edit it.
When is this useful?
If the same assignees are involved in the majority of a project's tasks, it's convenient to set a list of assignees at the project level. This saves time when creating tasks in the future. The assignees you need will be added to the task by default.
Having default project assignees doesn't guarantee that these assignees will see all of a project's tasks, since task creators can exclude certain assignees from the list manually when creating a task.