We have completed the checklist feature as a solution for this.
Here is a related thread if you’d like to support or follow the suggestion for assigning checklist items: https://planner.uservoice.com/forums/330525-microsoft-planner-feedback-forum/suggestions/14924745-assign-checklist-item-to-specific-individuals
An error occurred while saving the commentEryk Krzaczynski commented
Agree with the crowd here. The lack of ability to assign checklist items to team members and also without due dates makes them pretty useless. This was apparent in our first attempt at using planner.