Hi tangobango, thanks for your comments.
The feature to keep active the labels to enable drilling down is not included at now by the native Google Chart editor, when they will make it avaliable I will update my plugin.
At the moment, if you go to http://www.chartboot.com yuo can obtain the code of your chart and complement it manually with the custom code you can write reading the Google Charts tools documentation (i.e., here you have the events available for the pie charts https://developers.google.com/chart/interactive/docs/gallery/piechart#Events
Center the title is not possible at now.
You can label the y axis by selecting the verticalaxis (under Customize->Axis) and by setting a title.
Use Chart Title instead of ChartName (it's not transferred to the chart).
Regards,
lpagg