How do I dock a resizable ExtJS Ext.Panel within another resizable docked panel

I have a Modern ExtJS Ext.Panel docked left with resizable set with edge 'east'. IN this left panel, I want

Flex upper panel
docked bottom panel with edge 'north' within the docked left panel.

The "flex" upper left panel does not flex. See Sencha fiddle

Solution

Just turned out that the docked left panel needed a layout: 'vbox'.

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