My Lists has now been renamed to Spaces. Why? We know work is more than just a list of tasks. It can be a complete project, bugs, a customer CRM, client information or a marketing plan. We wanted to create a space for all types of work. Spaces function just like My Lists did, and interact with your Slack channels in the same way. The /mytodo list and /todo list commands still work with Spaces.
As what used to be called "Sub-lists" are now the only lists, they have been renamed Lists. They also function in the same way - the name has simply changed.