is it possible to create a new style format?

like, create a new button that will insert arbitrary code, like, say a link that has a specific class already attached?

yeah. You’ll have to hack the quicktags.js file in the wp-admin directory. I did so to add a button that inserts a link with a rel=”external” (how my external links are marked for some scripting tricks). My code was just this:
edButtons[edButtons.length] =
new edButton('ed_xtnl'
,'xlink'
,'<a href="https://" rel="external" title="Opens in a new window">'
,'</a>'
,'x'
);

All that really does is throw the empty anchor tag in the box when you click the button once, and closes it on the second hit. Whee.

podz’s guide may help:

https://www.tamba2.org.uk/wordpress/quicktags/

Many thanks guys! I’m no programmer but I will give it a try. How to bring the new button onto the quicktags menu?

cheers

Frank