add simple split and merge option

static/css/main.css

@@ -0,0 +1,36 @@
+.div_float_clear {
+    clear: both;
+}
+
+/* The snackbar - position it at the bottom and in the middle of the screen */
+#snackbar {
+    visibility: hidden; /* Hidden by default. Visible on click */
+    min-width: 800px; /* Set a default minimum width */
+    margin-left: -400px; /* Divide value of min-width by 2 */
+    background-color: #333; /* Black background color */
+    color: #fff; /* White text color */
+    text-align: center; /* Centered text */
+    border-radius: 2px; /* Rounded borders */
+    padding: 16px; /* Padding */
+    position: fixed; /* Sit on top of the screen */
+    z-index: 1; /* Add a z-index if needed */
+    left: 50%; /* Center the snackbar */
+    bottom: 30px; /* 30px from the bottom */
+}
+    
+/* Show the snackbar when clicking on a button (class added with JavaScript) */
+#snackbar.show {
+    visibility: visible; /* Show the snackbar */
+    /* Add animation: Take 0.5 seconds to fade in and out the snackbar.
+    However, delay the fade out process for 2.5 seconds */
+    /*
+    -webkit-animation: fadein 0.5s, fadeout 0.5s 2.5s;
+    animation: fadein 0.5s, fadeout 0.5s 2.5s;
+    */
+}
+
+@media (min-width: 992px) {
+    .nav-item.active {
+        border-bottom: 1px solid var(--bs-nav-link-color);
+    }
+}