Or just remove the date from a task? I can't drag or drop the tasks away from the planner.
If you want to shift that task in the list of a board you do it from edit side bar as shown in the gif below. Then you can remove the task from the week :
You need first assign a list then you can remove it.
I am assuming you have created that task on the planner (Schedule) on a specific date. Let me know if I am not correct. A task can be in a Board's list, Roles's list, Plan of the Week, Objectives, or in Schedule(Planner). You can move a task from any list( Board's list, Roles's list, Plan of the Week, Objectives) to a date by assign the date or date and time ie,. you can schedule a task. In another case you can move a task from scheduler to any list.
For removing date from a task(if you don't want to delete it) you should know where you want to move that tasks and assign it a place (objectivs / Board list). Let me know if it doesn't help.
Customer support service by UserEcho