I was wondering if you could add the option to add checkboxes to a document. This would allow us to make to do lists you can actually check off. That is the only thing I think is missing. Thanks!

An idea somewhat like this was dabbled in ages ago but it always felt kind of strange and so was never refined and included. What most people do for marking completion is to use the built-in Status or Label markers. Either one works well. Since these can be shown in both the Corkboard and Outliner (and labels can be shown in the binder too, in two different tinting fashions), they are both highly visible and easy to use individually or in bulk.

Check out this thread as an example.

And this one.