Chronological vs. Free Checklists
There are two progression types in checklists.
A "Chronological" progression is one that forces users to finish tasks one at a time.
This means users will not be able to advance to the next task in the checklist until they are done with the current task at hand.
On the other hand, the "Free" progression type lets users freely complete tasks without following a specific order.
You can set the progression type using the widget settings as shown below.