Use the existing toolbox design

osu.Game/Rulesets/Edit/ScrollingToolboxGroup.cs

@@ -0,0 +1,32 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Framework.Graphics;
+using osu.Framework.Graphics.Containers;
+using osu.Game.Graphics.Containers;
+
+namespace osu.Game.Rulesets.Edit
+{
+    public class ScrollingToolboxGroup : ToolboxGroup
+    {
+        protected readonly OsuScrollContainer Scroll;
+
+        protected override Container<Drawable> Content { get; }
+
+        public ScrollingToolboxGroup(string title, float scrollAreaHeight)
+            : base(title)
+        {
+            base.Content.Add(Scroll = new OsuScrollContainer
+            {
+                RelativeSizeAxes = Axes.X,
+                Height = scrollAreaHeight,
+                Child = Content = new FillFlowContainer
+                {
+                    RelativeSizeAxes = Axes.X,
+                    AutoSizeAxes = Axes.Y,
+                    Direction = FillDirection.Vertical,
+                },
+            });
+        }
+    }
+}