you can disable or make tooltip popup transparent by entering ' tooltips ' in compiz opacity plugin. but would be nice to be able to completely turn tooltips on and off, have them on by default but option to turn off.
You can do this through dconf-editor and look at the gwd settings
Google Web Designer??
Gtk-window-decorator
I thought the op was referring to tooltips generated by compiz. If you want a more system wide setting then this used to be possible with gtk 2. See https://ubuntuforums.org/showthread.php?t=1516052&page=2&p=10247075#post10247075