Unsolved Customize icon size for branch icon in QTreeWidget and QMenuBar

[HeFa]

I have not been able to change the size for the icon used for showing wether the branch is opened or closed in a QTreeWidget.
I've tried both with width/height and icon-size but nothing happens. It's always the same size(very small) for the icon.

The same is for an action on the menubar. The size seems to be fixed whatever I try in the stylesheet file.

Simple sample project