Thanks for your reply @Earthealthy_GIS 
Appreciated. Yes. This is one of the first thing I tried. But it failed. Because adding myself in the Attendees only send email notifications after a new Event is created or on Event change(s). This is useful. But this is not what I need.
What I need is this, when creating or editing a Lightning Calendar Event, to somehow being able to automatically send email reminder(s) before an event starts. For example, but not limited to, 1 hour before.
Maybe my question and the steps above were not clear. To clarify my question, I created this new question and new screenshots at Before a Thunderbird Lightning event starts, how to send an email reminder(s)? | Thunderbird Support Forum | Mozilla Support
According to Wayne, this Discourse is no longer actively monitored for Thunderbird support, discussion and suggestions. Source at https://discourse.mozilla.org/t/active-thunderbird-support-and-forums-read-me/113074
For those interested in this question about automated email notification, I suggest that we resume discussion at Before a Thunderbird Lightning event starts, how to send an email reminder(s)? | Thunderbird Support Forum | Mozilla Support