Loading a Checklist Template
Click on the … menu for the Checklist.
Select Load templates.
Use the checkboxes to indicate the template(s) you want to add to the issue. If there are more than ten templates in the project there will be a search bar you can use to find the desired template.
Click Load template(s). The selected templates will be added to the issue.
If the issue already has a checklist, you will be asked whether you want to append or overwrite the existing checklist. If you select Append, the template's items will be added to the end of the existing checklist. If you select Overwrite, all preexisting checklist items will be deleted prior to applying the template.