You can create Task not associated with Note in the following way.

※Tasks that are not linked to a note will be made available to all “Administrator” and “Member” permissions who have joined the team.

※Those with “Restricted Member Authority” and “1 Folder Guest Authority” can only view tasks that are not linked to a notebook for which they are the “Requester” or “Person in Charge”.

＜Desktop＞

1. Click “Tasks” on header.

2. You can create Task not associated with Note from “+Create a Task” button in the upper right corner of All Tasks page.

＜Mobile＞

1. Tap “Tasks” on footer.

2. You can create Task not associated with Note from “+” button on header.

Check this article about how to create Task associated with Note.