while playing with the config option i tried to achieve the region collapsable but change the behavior on runtime.

Why is getCollapseEl private? This would helpful to configure the region collapsable but hide the collapseEl on runtime.

Also i found a bug, when configuring
collapsible: false,
collapseMode: 'mini',
the collapse tool is shown and panel can be collapsed, but throws an error:
c.getComputedStyle(g.firstChild.firstChild, null) is null