Allow definition for lists.

cadetblue says:
It could be nice to attach to static lists (not the smart ones) a user defined definition (a text field) that will help to define accurately what is the meaning of the list and what tasks are supposed to be inserted in that list. This will support a disciplinated approach useful for single user but really useful for teams sharing lists, avoiding mismatches and doubts.

cadetblue says:
I was forgotting to add: the definitions could be shown as hintboxes when "mousing over" the tabs