Shared Lists
I'm really disappointed that this application has not supported the feature to allow shared lists. I use Wunderlist now and honestly have not made the change to To-Do because of this. I use it at work and collaborate with my work colleagues have access to the same lists for a number of things and then my wife and I both have access to some of the lists so we can both update. If she needs to make a grocery store list, it's automatically populated to my phone so I can swing by the store on the way home from work. Or if I need something, I can go into the list and add it so she sees it the next time she's at that store.
I just find it hard to believe this feature was dropped when we are collaborating more and more online and there are even other Microsoft 365 applications which all link together to make collaborating easier. This would be such a lovely extension of that if it was all tied together.