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Go to: Settings → Issues → Custom Fields → Create Custom Fieldscustom field
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As our fields are based on the new field types you can create as many fields as you need, add specific names for them, and configurations that represent your needs. For example, you can create several fields of the type ‘User Notification' and naming and configure them specifically for the project’s needs.
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Click 'Edit custom field config' and proceed with the direct field configuration, additional information you can find in the Using Fabulous Custom Fields section.
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That all, simple and usually like general Jira fields, now you can get experience with the field in the corresponding issue screen view.