Every task can have a unlimited number of checklist items.
To add a new checklist item, simply click on the + button next to "Add Checklist Item" in the task detail dialog.
You can check off items as soon as they are finished, or simply delete them by clicking the X button on the right side of the item.
Checklists can be saved to your account and be used as templates on another task.
Click on the small triangle next to "Add Checklist Item" to save, load or delete checklists.
Paste a list of todos into a checklist item and select "Split into separate items" to automatically create multiple checklist items out of your list.