update

src/sass/gnome-shell/common/_overview.scss

@@ -1,4 +1,21 @@
 
+%overview_scrollbar {
+  StBin#trough {
+    background-color: on($osd, divider);
+  }
+
+  StButton#vhandle, StButton#hhandle {
+    background-color: on($osd, disabled);
+    &:hover { background-color: on($osd, secondary); }
+    &:active { background-color: on($osd); }
+  }
+}
+
+#overview {
+  spacing: 24px;
+  StScrollBar { @extend %overview_scrollbar; }
+}
+
 .overview-controls {
   padding-bottom: $base_padding * 5;
 }

src/sass/gnome-shell/common/_scrollbars.scss

@@ -9,21 +9,22 @@ StScrollBar {
   padding: 0;
 
   StScrollView & {
-    min-width: 16px;
-    min-height: 16px;
+    min-width: 12px;
+    min-height: 12px;
   }
 
   StBin#trough {
-    margin: 6px;
     border-radius: $circular_radius;
     background-color: $divider;
+    margin: 3px;
   }
 
   StButton#vhandle, StButton#hhandle {
     border-radius: $circular_radius;
     background-color: $text-disabled;
-    //border: 4px solid transparent; //would be nice to margin or at least to transparent
-    margin: 6px;
+    border: 3px solid transparent; //would be nice to margin or at least to transparent
+    margin: 3px;
+
     &:hover { background-color: $text-secondary; }
     &:active { background-color: $text; }
   }

src/sass/gnome-shell/widgets-3-28/_overview.scss

@@ -1,17 +1 @@
 
-%overview_scrollbar {
-  StBin#trough {
-    background-color: on($osd, divider);
-  }
-
-  StButton#vhandle, StButton#hhandle {
-    background-color: on($osd, disabled);
-    &:hover { background-color: on($osd, secondary); }
-    &:active { background-color: on($osd); }
-  }
-}
-
-#overview {
-  spacing: 24px;
-  StScrollBar { @extend %overview_scrollbar; }
-}