Hi Jim,
Thanks for reaching out here. Good question -- the To-Do List source is a bit unique.
It sounds like your To-Do List source has been modified in some way. The $$sc_EditEventsInFileMaker setting might be set to False for the To-Do List source, so that editing To-Dos happens in DayBack's built-in popover. "Out of the box", that setting is True, and editing the To-Dos happens in a separate FileMaker window. If you make changes to a To-Do there, the calendar would update when you close the window, but you would not see the "Saved" message at the bottom of the calendar (since the record was saved in another window already).
And you're right; ToDos don't have a ContactID field. The "To-Do Details" layout (where you would normally edit To-Dos out of the box) doesn't have a field for linking a contact. Using that layout instead of the built-in popover is probably the best option for the To-Do List source, since it comes with other customizations around its date due and date done. (If you wanted, you *could* use the built-in popover for the To-Do List source, either hiding that contact field on the popover, or creating and mapping a new ContactID field on the source. But note what makes the To-Do List source unique:
https://www.seedcode.com/pmwiki/index.p ... .To-DoList)
I hope that helps! Keep us posted with any other questions.