QTreeWidget change controll size for collapse or expand children

[qt_done]

Hello everybody,

I'm new here and I hope to get help for my problem with Qtreewidget.

I'm using a qtreewidget for displaying information in an android-app.
But the "default" control for expand or collapse children is a bit too small for touching with my fingers.
So it's very hard to focus the control.

So, is it possible to make the control bigger for easier touching? Maybe with stylesheet?

Thanks for help :)