Invite and it is theirs too
Send an invite. The other person opens the list with everything already in it, and from then on you are both working from the same one.
Features
Lists you share with the people they involve
Most shared work does not need a project tool. It needs both people looking at the same list.
Everyone sees the same next thing
The list shows what is due and what is next, identically for everyone in it. That removes most of the messages that begin with "any update on".
As many lists as the situation needs
One for the house, one for the team, one for the trip. There is no limit, and a list can start private and become shared the moment it needs to.