It would be useful to be able to change the background colour and transparency of the tooltip to highlight and colour-code, and to allow parts of the visual to be seen behind it. The latter would be ...
I would also love having ability to have different tooltip based on the visual context. e.g possibility to have a tooltip specific to a "category column" of a matrix and another one different when hovering on the summarized values. For now you can only have one tooltip for a given visual.
