diff --git a/css/customstyles-precice.css b/css/customstyles-precice.css
index 06e40be4a4..354a291f73 100644
--- a/css/customstyles-precice.css
+++ b/css/customstyles-precice.css
@@ -350,4 +350,33 @@ div.tab-content {
   }
 div.tab-content div.tab-pane pre {
   margin-top: 0px;
-}
\ No newline at end of file
+}
+}
+
+/* Hide default marker Chromium/WebKit */
+details > summary::-webkit-details-marker {
+  display: none !important;
+}
+
+/* Hide default marker in Firefox */
+details > summary {
+  list-style: none;
+  cursor: pointer;
+  position: relative;
+  padding-right: 1.2em;
+}
+
+/* closed */
+details > summary::after {
+  content: "▼";
+  position: absolute;
+  right: 0;
+  top: 50%;
+  transform: translateY(-50%);
+  font-size: 0.9em;
+}
+
+/* open */
+details[open] > summary::after {
+  content: "▲";
+}