For example I would like to add the default field [EVENT_NAME]. Or the custom field [BIRTHDATE].
Point is: changes I make in the editor Joomla, even if it's just plain text, are not saved. No errors are shown. So I can't make a screenshot of anything.
Please answer my question: can I make changes in the editor in Joomla (if yes, there is a bug) OR should I change the HTML outside of Joomla and then copy/paste new code to the Invoice template?