shadcn-ui/apps/v4/examples/base/resizable-nested.tsx

import {
  ResizableHandle,
  ResizablePanel,
  ResizablePanelGroup,
} from "@/examples/base/ui/resizable"

export function ResizableNested() {
  return (
    <ResizablePanelGroup direction="horizontal" className="rounded-lg border">
      <ResizablePanel defaultSize={50}>
        <div className="flex h-[200px] items-center justify-center p-6">
          <span className="font-semibold">One</span>
        </div>
      </ResizablePanel>
      <ResizableHandle />
      <ResizablePanel defaultSize={50}>
        <ResizablePanelGroup direction="vertical">
          <ResizablePanel defaultSize={25}>
            <div className="flex h-full items-center justify-center p-6">
              <span className="font-semibold">Two</span>
            </div>
          </ResizablePanel>
          <ResizableHandle />
          <ResizablePanel defaultSize={75}>
            <div className="flex h-full items-center justify-center p-6">
              <span className="font-semibold">Three</span>
            </div>
          </ResizablePanel>
        </ResizablePanelGroup>
      </ResizablePanel>
    </ResizablePanelGroup>
  )
}