By default, only the Project lead, the JIRA System administrators and users in project role administrators are enabled to setup approval steps for a specific issue.
You can the default grants via the Permission Administration screen .
TheConfigure Approval for Single Issuescreen let you setup approval steps for a specific issue.
When configuring the approval workflow for a single issue, this setting overrides
Approval Mappings can be override by a configuration applied on single issue via the Issue Approval Configuration screen.