Issue #3513925 by goz: Multiple modals stay on top of backdrops

assets/css/component/dialog.css

 .modal-footer .ui-dialog-buttonset {
   gap: var(--bs-modal-footer-gap);
 }
+
+.modal {
+  --bs-modal-zindex: 1050;
+}

assets/js/misc/dialog/dialog.js

@@ -225,6 +225,11 @@
       if ($element.modal !== undefined) {
         $element.modal(settings);
         $element.modal('show');
+        // Be sure modal is last, it will be on top of all other modals and
+        // backdrops.
+        // Thanks to that, no more need different z-index for modals and
+        // backdrops.
+        $element.appendTo('body');
       }
 
       if (settings.width) {

ui_suite_bootstrap.libraries.yml

@@ -50,12 +50,13 @@ drupal.dialog:
   js:
     assets/js/misc/dialog/dialog.js: {}
   css:
-    component:
+    theme:
       assets/css/component/dialog.css: {}
   dependencies:
     - core/jquery
     - core/drupal
     - core/drupalSettings
+    - ui_suite_bootstrap/bootstrap
 
 drupal.dialog.ajax:
   js: