update

src/_sass/gtk/apps/_gnome-3.22.scss

@@ -1857,9 +1857,14 @@ window.background.csd {
     }
   }
 
-  > stack > box > box > list { // ArcMenu setting sidebar
+  > stack > box > box > list,
+  > stack > box > stack > scrolledwindow > viewport > list { // ArcMenu setting sidebar
     border-bottom-left-radius: $window-radius;
   }
+
+  > stack > box > .sidebar > scrolledwindow > viewport > list {
+    padding: 0 0;
+  }
 }
 
 /***********

src/_sass/gtk/apps/_misc.scss

@@ -330,4 +330,12 @@ window.background.csd {
       }
     }
   }
+
+  > box.vertical > overlay > stack > scrolledwindow.frame {  // >= 10.0
+    border: none;
+
+    > viewport.frame > box.vertical > stack > scrolledwindow {
+      border-top: 1px solid $divider;
+    }
+  }
 }

src/gtk/3.0/gtk-dark.css

@@ -5668,10 +5668,15 @@ window.background.csd > stack > grid > scrolledwindow > viewport > box > frame >
   border: none;
 }
 
-window.background.csd > stack > box > box > list {
+window.background.csd > stack > box > box > list,
+window.background.csd > stack > box > stack > scrolledwindow > viewport > list {
   border-bottom-left-radius: 18px;
 }
 
+window.background.csd > stack > box > .sidebar > scrolledwindow > viewport > list {
+  padding: 0 0;
+}
+
 /***********
  * Dialogs *
  ***********/
@@ -6065,6 +6070,14 @@ window.background.csd > box.vertical > overlay > stack > box.vertical > box.hori
   border-radius: 0;
 }
 
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame {
+  border: none;
+}
+
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame > viewport.frame > box.vertical > stack > scrolledwindow {
+  border-top: 1px solid rgba(255, 255, 255, 0.12);
+}
+
 /*********
  * Unity *
  *********/

src/gtk/3.0/gtk-light.css

@@ -5667,10 +5667,15 @@ window.background.csd > stack > grid > scrolledwindow > viewport > box > frame >
   border: none;
 }
 
-window.background.csd > stack > box > box > list {
+window.background.csd > stack > box > box > list,
+window.background.csd > stack > box > stack > scrolledwindow > viewport > list {
   border-bottom-left-radius: 18px;
 }
 
+window.background.csd > stack > box > .sidebar > scrolledwindow > viewport > list {
+  padding: 0 0;
+}
+
 /***********
  * Dialogs *
  ***********/
@@ -6064,6 +6069,14 @@ window.background.csd > box.vertical > overlay > stack > box.vertical > box.hori
   border-radius: 0;
 }
 
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame {
+  border: none;
+}
+
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame > viewport.frame > box.vertical > stack > scrolledwindow {
+  border-top: 1px solid rgba(0, 0, 0, 0.12);
+}
+
 /*********
  * Unity *
  *********/

src/gtk/3.0/gtk.css

@@ -5668,10 +5668,15 @@ window.background.csd > stack > grid > scrolledwindow > viewport > box > frame >
   border: none;
 }
 
-window.background.csd > stack > box > box > list {
+window.background.csd > stack > box > box > list,
+window.background.csd > stack > box > stack > scrolledwindow > viewport > list {
   border-bottom-left-radius: 18px;
 }
 
+window.background.csd > stack > box > .sidebar > scrolledwindow > viewport > list {
+  padding: 0 0;
+}
+
 /***********
  * Dialogs *
  ***********/
@@ -6065,6 +6070,14 @@ window.background.csd > box.vertical > overlay > stack > box.vertical > box.hori
   border-radius: 0;
 }
 
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame {
+  border: none;
+}
+
+window.background.csd > box.vertical > overlay > stack > scrolledwindow.frame > viewport.frame > box.vertical > stack > scrolledwindow {
+  border-top: 1px solid rgba(0, 0, 0, 0.12);
+}
+
 /*********
  * Unity *
  *********/