In GTO, every task is part of one list, and every list is linked to one account. You can have any number of lists in each account, and any number of tasks in each list (for performance reasons, though, it's best to keep lists to less than 1000 tasks).
When you delete a list in GTO, it will also be removed from the server. The default list for each account (the first list that was automatically created in Google Tasks with a name like "John's List") cannot be deleted, due to a restriction on the Google Tasks server. You also cannot delete every list in GTO's offline account, but you can hide the offline lists.
When you delete a list, GTO saves it in the local database. As long as you don't delete the associated account or uninstall GTO, you can recover your deleted lists and all their tasks. Read about the Undelete List option on the Lists preference page.
GTO allows you to move a list, and all its tasks, to a different account. In the current version, this process appears to freeze GTO for a few seconds. GTO will still be moving the list in the background, so wait a moment to let it finish.
When GTO is opened, it normally displays the list that was most recently displayed. To view a different list, select the list button in the lower-left corner.
You can also swipe to the left or right to view the next or previous list. To change the senstivity of this swipe, see the Behavior menu.
If you open GTO by clicking the widget, it will open to the list shown on the widget by default. This behavior can be changed by selecting a different click action in the widget settings.
GTO contains a special page that displays all your tasks together. You can navigate to it by selecting All Lists when choosing a list to view. When the Collapse Lists preference is disabled, you can sort all your tasks together on this page, as though they were all in the same list. With Collapse Lists enabled, each list will be sorted individually, and the tasks for a certain list can be hidden by collapsing the list name. Next to each list name is the number of completed tasks and the number of total tasks in that list.