Theme mouse action's active nav item to point on it's configuration.

sass/style.scss

@@ -127,7 +127,29 @@
 .mouse {
   &__action {
     &--type {
-      border-right: 1px solid #000;
+      .nav {
+        border-right: 1px solid #ccc;
+
+        li.active {
+          a {
+            border-top-right-radius: 0;
+            border-bottom-right-radius: 0;
+
+            &:after {
+                content: '';
+                display: block;
+                position: absolute;
+                width: 0;
+                height: 0;
+                top: 0;
+                right: -4rem;
+                border-color: transparent transparent transparent #337ab7;
+                border-style: solid;
+                border-width: 2rem;
+            }
+          }
+        }
+      }
     }
 
     &--config {