HERE IS HELP:
Since Thunderbird 68 - You can use your Stationery files with SmartTemplate4. Simply open SmartTemplate settings and select "File Templates" from the Accounts dropdown; you can then add your Stationery files to the write, reply and forward buttons. I have been using Stationery for years and worked with the author Arivald to make both our Add-ons compatible with each other.
Since he has no time to work for nothing for the many weeks that it takes to update Addons to the latest Tb version I decided to incorporate the Stationery feature into my own Add-on, because external templates are absolutely crucial for a productive Mail environment. Stationery has always been a 5 star Add-on, absolutely important.
I am programming Add-ons for 10 years and I would have patched Stationery if I had a month of free time (I seriously tried). But I had to set my priorities and look after my own Add-ons.
Full disclosure: SmartTemplate4 requires a license (5$ / year) because it is impossible to work on Add-ons every day of the week for nothing. All "free as in beer" things will end eventually, because they exploit people.
It was a great and useful Add-on - but unfortunately is not compatible with Tb 68 - if you want to keep working with external HTML files, please try out my Add-on SmartTemplate4 instead - this supports external html files from version 2.3.
Thanks for supporting the SmartTemplate4 Addon in 0.8! This made both addons even more useful! I can now use fully styled html templates and the convenient user interface of selecting templates via single-click; whilst using the powerful variables available in SmartTemplate4. Definitely a very useful productivity tool.
With Stationery+ST4, it is very easy to set up form letters such as support replies and save tons of time when replying to support mail. We are thrilled about this new version.
This is indispensable. Excellent replacement for signatures (which are a bit weak in Thunderbird). Also the HTML editor is really worth its weight in gold. It is a total time saver for standard replies (template).
Also support is very good and the author is open to good suggestions. Love the font preview feature - I didn't even know it was supplied by you, as I have been using Stationery for a long time now.
This is super useful for 2 reasons:
you can create template replies for repeating answers, so it is great for support or donation mail.
the built in HTML source view. This is simply a must in order to create great looking emails without resorting to an external editor. Supports everything gecko8 supports, so it is CSS3, including border radius, gradients, transitions, anything that would make a web site look nice, now also in my emails.
thanks for a great extension.