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When a template is applied to an issue a separate copy of the template is added to the issue (as opposed to being linked to or referenced by the issue). If a template is later deleted from the templates list, copies of template that have been added to issues will remain.

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To manually add a template to an issue:

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name	LoadTemplates

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 templates. 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.

Adding Templates Automatically (Default Templates)
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DefaultTemplate
DefaultTemplate

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	Setting a Default Template
	Setting a Default Template

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isMissingRequiredParameters	LabelTemplates
	trueLabelTemplates

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In Issue Checklist Pro, you can automatically add templates based on a value in the Jira labels field. To add a template based on a label.

Ensure that the Apply checklist templates from issue labels global setting is enabled.
Ensure that the template name does not include any spaces.
Add a label (when creating or editing the issue) that exactly matches the name of the template (case sensitive).
The template will be added to the issue. Note that removing the label will not remove the template once it has been applied.

Note
If you remove and add a label (having a corresponding template) multiple times, checklist template will be applied every time you add the label, thus checklist items can get duplicated.

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To apply a template in bulk:

Ensure that the Save checklist data to Jira custom fields global settingis enabled.
Temporarily add the Checklist Template field to the Edit issue screen.
Use JQL to select the issues you want to add the template to.
Click on the … menu and select Bulk change all x issues.
Use the checkboxes to select the issues you want to add the template to. Click Next.
Select Edit issues and click Next.
Select Change Checklist Template and use the dropdown to select the indicated template. Click Next.
Click Confirm.
Click Done when the update is complete.