Yes, if you create a list yourself, you have also created a group. Within this group you can create several lists.
No, we do not want to store more than necessary. Each group or list has a unique key. Everyone who has the key can edit the list or the whole group.
Yes, we use cookies so that you can see your lists and groups directly when you enter. You should save your keys. You can save them, for example, by simply bookmarking them in your browser when a list or group is displayed.