1<PanelGroup>
2    <Panel minSize={10} defaultSize="100px">
3      left
4    </Panel>
5    <PanelResizeHandle />
6    <Panel minSize={20} defaultSize={30}>
7      middle
8    </Panel>
9    <PanelResizeHandle />
10    <Panel minSize={20} defaultSize={40}>
11      right
12    </Panel>
13  </PanelGroup>