How to Hide the “Configure Fields” Button on the Create Issue Screen in JIRA

Copy this code in the description of a custom field (in the Field Configuration linked to the project)

<script type="text/javascript">
(function($) {
    AJS.toInit(function(){
        // init on load
        AJS.$("#qf-field-picker-trigger").hide();
    })
    JIRA.bind(JIRA.Events.NEW_CONTENT_ADDED, function (e, context) {
        // init on refresh
        AJS.$("#qf-field-picker-trigger").hide();
    });
})(AJS.$);
</script>

Result: