I have created an add-on sidebar: https://developers.google.com/gsuite/add-ons/cats-quickstart
I use that to send an email, so I have created an email template. So far so good. Inside my email template there is button. What I need, is that when the user clicks that button I want to open the add-on (sidebar).
I can’t find anything on Google documentation, so I am not sure if that’s possible or not. So I would appreciate any suggestions