It is possible to leave comment on parent tasks, to store some extra user data about the tasks.
In the web UI you can view and edit the comment by clicking on edit on the Comment panel. That will open a small editor, where you can write your comment.
The comment can be formatted with HTML, so you can have different styles and formats.
It is also possible to add the comment from the Grasshopper plugin. You can do it in the Project and Task component, by applying an override like this:
{"comment": "this is my comment"}