In addition to separators, users can split items into groups by creating separate checklists, each with its own name and progress bar:
You can rename any checklist, however, the default checklist can be renamed only if there is at least one other checklist.
The option to create multiple checklists is disabled by default.
It needs to be explicitly enabled on the settings page. To go there, navigate to Jira settings >> Apps >> Issue Checklist >> Global Settings.
When multiple checklists and custom fields sync are enabled at the same time, Checklist Content YAML field is ignored.
Instead, use Checklist Text field - it will contain all checklists and items in given issue.
There is a limit for the number of items per issue in Issue Checklist Free as explained on the comparison page.
The limit applies to the total number of items in an issue, regardless of how the items are distributed among multiple checklists.
If you don't want the button to be displayed simply enable and then disable multiple checklists option.
The "Add checklist" button will become visible after the multiple checklists option is enabled again.