By default, during issue creation and issue edit, the "Configure Fields" button will be shown on the top right corner of the pop up (refer to the screen capture below). Some administrator would prefer to hide the button to prevent the users from changing the pre-configured fields.

Hiding Jira "Configure Fields" Button without restart

1. For the javascript to run, you will need to paste the coding on the description area of the field since it supports html codings. To do this, actually you have two choices, you can either create a custom field or utilizing a default field on the screen.
2. Similar steps are applicable to both default field or custom field after you created a custom field. However do note that, if you used a custom field, the custom field will be visible to the users and hiding it from Field Configuration will disable the javascript pasted on its description.
3. Navigate to Administration > Issues > Fields > Fields Configurations > Configure to view the list of fields.
4. Choose the field that you wanted to paste the codes on (recommended to paste on Description Field or Comment Field since both of them is without pre-defined descriptions on them).
5. Click on edit to show the Field Description.

6.  Paste the codes provided below to the Description field and Update the field.

   Jira 8 and lower:

   <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>

   
   

   Jira 9+ must use the script type module due to it deferring the scripts loading:

   <script type="module">
   (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>

7. After doing this, you can verify the result by trying to create an issue, the button "Configure Fields" should not be visible anymore. (Refer screen capture below)