Ciao Alex!
Sadly there is no way to control that in the configuration, as the position of the balloon is controlled by Google Earth, whcih calculates the best possible position according to your screen resolution and where you clicked in the placemark (plot)
The best approach is to move the plot to one side of the Google Earth viewframe (i.e. left or top) and click on the opposite side of the plot (i.e. righ or bottom ) close to its border, so that the balloon will appear in such a way that does not hide the plot!
Check out these examples:
![alt text][1]
![alt text][2]
[1]: http://www.openforis.org/support/upfiles/googleearth_2020-11-30_09-09-23.jpg
[2]: http://www.openforis.org/support/upfiles/googleearth_2020-11-30_09-17-07_1.png