Variables are surrounded by {}, and initial (default) templates are
generated on demand from the plaintext version of emails. The custom
emails are intended to only be used if the user actually changes them,
as they lose the features of the default ones, such as tables.
After selecting users in the accounts tab, you can press 'Announce',
then write a subject and message (with markdown), and an email will be
sent to each selected user.
Harvey Tindall