My preference is set on Informant and the link does show up but unlike the Apple Calendar it is not ‘live’. If I click the link in Apple Calendar it takes me to Agenda but when I click the link in Informant nothing happens.
Does Informant support clickable links in the notes field of an event at all? For example, does entering http://apple.com in the notes field work? If not it’s best to contact their support to ask for them to allow for clickable links.