add horizontal handlebars

res/css/structures/_MainSplit.scss

@@ -26,3 +26,23 @@ limitations under the License.
     margin: 0 -10px 0 0;
     padding: 0 10px 0 0;
 }
+
+.mx_MainSplit > .mx_ResizeHandle_horizontal:hover {
+    position: relative;
+
+    &::before {
+        position: absolute;
+        left: 4px;
+        top: 50%;
+        transform: translate(0, -50%);
+
+        height: 30%;
+        width: 4px;
+        border-radius: 4px;
+
+        content: ' ';
+
+        background-color: $primary-fg-color;
+        opacity: 0.8;
+    }
+}

res/css/structures/_MatrixChat.scss

@@ -78,3 +78,23 @@ limitations under the License.
     */
     height: 100%;
 }
+
+.mx_MatrixChat > .mx_ResizeHandle_horizontal:hover {
+    position: relative;
+
+    &::before {
+        position: absolute;
+        left: -2px;
+        top: 50%;
+        transform: translate(0, -50%);
+
+        height: 30%;
+        width: 4px;
+        border-radius: 4px;
+
+        content: ' ';
+
+        background-color: $primary-fg-color;
+        opacity: 0.8;
+    }
+}