I have multiple pages, but one of them will automatically add the checkbox to a new item added at the top of the list/page but not the others. Is there a setting I can change to make this my default for all new items?
Are you adding items by hitting enter key? They always get the checkbox/no checkbox state the same as the preceding item. In case of adding item to the top of the list the preceding item is the page title. You can set the checkbox/no checkbox status of list title with shortcut for adding/removing checkbox (cmd+shift+c for mac ) - checkbox is not visible in title and there is no item in menu to set it with mouse clicks, but it works.