Additional functionality/usability for chart legends

In one of our current dashboarding solutions we appointed several pie charts as key elements to provide users with filtering options for other elements. While selecting and de-selecting pie chart allows for easy filtering in most cases, we noted trouble for our dashboard users in specific scenarios.

The following occured: There are instances in which an individual pie chart slice can become extremely hard to select and de-select because the connected value may currently be extremely small relative to other values of the same pie chart. This makes filtering by selection rather hard. While we can implement work arounds via buttons, we would like to propose a more elegant solution:

We noted that chart legends currently only provide information and no further functionality. That should be changed. We imagine using a chart legend for an indiviual chart element (such as a pie chart slice) like a button to select and de-select it, basically as an addition or alternative to selecting the actual chart elements. This would eliminate the difficulty of selecting chart elements that are extremely small compared to others and increase the general usability of charts.