Rated 5 out of 5 stars

Does not work in the latest version of Thunderbird 78.4.0, since the option to add text is missing when you go to 'Tools' - 'Add-on Options'.

Thanks for the feedback. It indeed works as described.

This review is for a previous version of the add-on (0.55). 

This was a change in Thunderbird (on which I has no influence ... I don't know why this was changed ...). Now you have to go to 'Tools' - 'Add-ons' - find the entry 'Standardtexter' - click on the 3 points on the right side - choose 'Options'.