You can add a task follower by including their @name (if they’re on your Slack team) or email address anywhere after the assignee’s name.
/sendtask @jason Buy milk on the way home tomorrow email@example.com
/sendtask Buy milk on the way home tomorrow @jason firstname.lastname@example.org
Both of these examples will create a task titled “Buy milk on the way home tomorrow” that is assigned to Jason and has a due date set to the next day. However, it will also include the task creator and Bart Simpson as followers in the task.
Note: If you want to assign the task to yourself and add collaborators, you have to include your @name or email address before you include any followers.