diff --git a/theme/boost/scss/moodle/tertiarynavigation.scss b/theme/boost/scss/moodle/tertiarynavigation.scss
index 0e5eed6b2bb..4bf69b5e60c 100644
--- a/theme/boost/scss/moodle/tertiarynavigation.scss
+++ b/theme/boost/scss/moodle/tertiarynavigation.scss
@@ -1,11 +1,37 @@
 .tertiary-navigation {
     padding-top: 10px;
 
-    .navitem {
+    &.full-width-bottom-border {
+        width: calc(100% + 1rem + 30px);
+        margin-left: calc(-0.5rem - 15px);
+        margin-right: calc(-0.5rem - 15px);
+        border-bottom: 1px solid $gray-300;
+        margin-bottom: 25px;
+
+        @include media-breakpoint-down(sm) {
+            width: calc(100% + 1rem);
+            margin-left: -0.5rem;
+            margin-right: -0.5rem;
+        }
+
+        .row {
+            margin: 0;
+            padding-left: 0.5rem;
+            padding-right: 0.5rem;
+        }
+    }
+
+    .navitem,
+    .navitem-divider {
         display: flex;
         margin-bottom: 25px;
     }
 
+    .navitem-divider {
+        width: 1px;
+        background-color: $gray-300;
+    }
+
     & > a.btn,
     & > div.urlselect {
         margin-bottom: 25px;
@@ -22,6 +48,11 @@
             font-weight: bold;
         }
     }
+
+    .navitem:not(:last-child),
+    .navitem-divider:not(:last-child) {
+        margin-right: 20px;
+    }
 }
 
 @media print {
diff --git a/theme/boost/style/moodle.css b/theme/boost/style/moodle.css
index 7120d1ba330..e2374574013 100644
--- a/theme/boost/style/moodle.css
+++ b/theme/boost/style/moodle.css
@@ -21741,9 +21741,28 @@ div.editor_atto_toolbar button .icon {
 
 .tertiary-navigation {
   padding-top: 10px; }
-  .tertiary-navigation .navitem {
+  .tertiary-navigation.full-width-bottom-border {
+    width: calc(100% + 1rem + 30px);
+    margin-left: calc(-0.5rem - 15px);
+    margin-right: calc(-0.5rem - 15px);
+    border-bottom: 1px solid #dee2e6;
+    margin-bottom: 25px; }
+    @media (max-width: 767.98px) {
+      .tertiary-navigation.full-width-bottom-border {
+        width: calc(100% + 1rem);
+        margin-left: -0.5rem;
+        margin-right: -0.5rem; } }
+    .tertiary-navigation.full-width-bottom-border .row {
+      margin: 0;
+      padding-left: 0.5rem;
+      padding-right: 0.5rem; }
+  .tertiary-navigation .navitem,
+  .tertiary-navigation .navitem-divider {
     display: flex;
     margin-bottom: 25px; }
+  .tertiary-navigation .navitem-divider {
+    width: 1px;
+    background-color: #dee2e6; }
   .tertiary-navigation > a.btn,
   .tertiary-navigation > div.urlselect {
     margin-bottom: 25px; }
@@ -21753,6 +21772,9 @@ div.editor_atto_toolbar button .icon {
     padding: 0;
     font-size: 1.4rem;
     font-weight: bold; }
+  .tertiary-navigation .navitem:not(:last-child),
+  .tertiary-navigation .navitem-divider:not(:last-child) {
+    margin-right: 20px; }
 
 @media print {
   .tertiary-navigation {
diff --git a/theme/classic/scss/moodle.scss b/theme/classic/scss/moodle.scss
index dede561fd1a..c83525746c2 100644
--- a/theme/classic/scss/moodle.scss
+++ b/theme/classic/scss/moodle.scss
@@ -17,3 +17,18 @@ img.userpicture {
         font-weight: bold;
     }
 }
+
+.tertiary-navigation {
+
+    &.full-width-bottom-border {
+        width: calc(100% + 2.5rem);
+        margin-left: -1.25rem;
+        margin-right: -1.25rem;
+
+        @include media-breakpoint-down(sm) {
+            width: calc(100% + 2rem);
+            margin-left: -1rem;
+            margin-right: -1rem;
+        }
+    }
+}
diff --git a/theme/classic/style/moodle.css b/theme/classic/style/moodle.css
index 85667cd7740..0dffd3c4d22 100644
--- a/theme/classic/style/moodle.css
+++ b/theme/classic/style/moodle.css
@@ -21687,9 +21687,28 @@ div.editor_atto_toolbar button .icon {
 
 .tertiary-navigation {
   padding-top: 10px; }
-  .tertiary-navigation .navitem {
+  .tertiary-navigation.full-width-bottom-border {
+    width: calc(100% + 1rem + 30px);
+    margin-left: calc(-0.5rem - 15px);
+    margin-right: calc(-0.5rem - 15px);
+    border-bottom: 1px solid #dee2e6;
+    margin-bottom: 25px; }
+    @media (max-width: 767.98px) {
+      .tertiary-navigation.full-width-bottom-border {
+        width: calc(100% + 1rem);
+        margin-left: -0.5rem;
+        margin-right: -0.5rem; } }
+    .tertiary-navigation.full-width-bottom-border .row {
+      margin: 0;
+      padding-left: 0.5rem;
+      padding-right: 0.5rem; }
+  .tertiary-navigation .navitem,
+  .tertiary-navigation .navitem-divider {
     display: flex;
     margin-bottom: 25px; }
+  .tertiary-navigation .navitem-divider {
+    width: 1px;
+    background-color: #dee2e6; }
   .tertiary-navigation > a.btn,
   .tertiary-navigation > div.urlselect {
     margin-bottom: 25px; }
@@ -21699,6 +21718,9 @@ div.editor_atto_toolbar button .icon {
     padding: 0;
     font-size: 1.4rem;
     font-weight: bold; }
+  .tertiary-navigation .navitem:not(:last-child),
+  .tertiary-navigation .navitem-divider:not(:last-child) {
+    margin-right: 20px; }
 
 @media print {
   .tertiary-navigation {