Calendar Chart - How can the tooltip be made to persist on mouseout?

[Maggie Capewell]

Hi! I set up a Google Calendar Chart using HTML tooltips. There are links included in the tooltip content. My question is, how can tooltips be made to persist so that a user can actually click on the link in the tooltip? I've tried adding 'trigger: "selection"' to the tooltip configuration options, but it doesn't do anything. Is this option not supported by the calendar chart? Thanks!