--Create class `grw-nav-slide-hr`

--Replace `#grw-nav-slide-hr` to `grw-nav-slide-hr` in scss.

src/client/js/components/PageAccessoriesModal.jsx

@@ -121,7 +121,7 @@ const PageAccessoriesModal = (props) => {
               onClick={closeModalHandler}
             />
           </Nav>
-          <hr id="grw-nav-slide-hr" className="my-0" style={{ width: `${sliderWidth}%`, marginLeft: `${sliderMarginLeft}%` }} />
+          <hr id="grw-nav-slide-hr" className="my-0 grw-nav-slide-hr" style={{ width: `${sliderWidth}%`, marginLeft: `${sliderMarginLeft}%` }} />
           <hr className="modal-split-hr m-0" />
           <TabContent activeTab={activeTab}>
             <TabPane tabId="pagelist">

src/client/styles/scss/_page_accessaries_modal.scss

@@ -8,7 +8,7 @@
       }
     }
   }
-  #grw-nav-slide-hr {
+  .grw-nav-slide-hr {
     border-top: 0rem;
     border-bottom: 3px solid;
     transition: 0.3s ease-in-out;

src/client/styles/scss/theme/_apply-colors.scss

@@ -291,7 +291,7 @@ pre:not(.hljs):not(.CodeMirror-line) {
     background-color: $bordercolor-nav-tabs;
   }
 
-  #grw-nav-slide-hr {
+  .grw-nav-slide-hr {
     border-color: $color-link;
   }
 }