In the current version the legends for charts containing groups and series has a flat list of the series for each group. This is unreadable and toggling is not of any use.

The suggested improvement is a legend containing groups (e.g.) sex and series (e.g. age 0-19, 29-39 etc). Toggling of groups should be provided. Toggling of series would also be useful, but less important than toggling groups.