Send email via a select

I’d like to set up a page (of users) where I could select several (or All) users that have emails.

Then click a button to compose, then send a mass email of those selected.

Is this possible within PHPmaker?

Read help file → Server Events and Client Scripts → Row_CustomAction server event example.

Is there a good place where I can dive into ALL of the commands that can be used with the server events?

It depends on which server event, for example, Row_CustomAction is a method of the page class, you may see the properties and methods in the generated source code of the table class and the page class in the “classes” folder.