Besides controlling sharing for the individual To Do List, you can also set sharing at the List Set level. List sets in To Do are equivalent to folders in Files. Whenever you set List Set sharing, all To Do Lists in that List Set (and any subsequently newly created To Do Lists) are automatically given the List Set's Share Settings.
How to share List Sets
Keep&Share gives you two levels of To Do List organization. The top-level is called a “List Set.” In new accounts, they have an initial default name of “List Set 1,” “List Set 2” etc. If you want to share a Folder Set of To Do Lists you'll need to click on the gear icon for your Folder Set in the Navigator. Follow the steps in the image below:
Be careful: The “Apply these share settings to all existing lists in this list set” box is checked by default. When it is checked, all of your To Do Lists in the List Set will receive the new sharing you specify for the List Set. It is a powerful way to erase or set new sharing on everything at once.
Click on the ”Can Edit” checkbox next to the names of individuals or on the checkbox at the top of the "Edit Rights" column to give Edit rights to everyone in your Share List at once. However, to guard against accidental deletion of important information, only *you* can delete an entire To Do List from the List Set.