I had a request today to to add WYSIWYG support to the transactional emails section under “System” > “Transactional Emails”.
It appears that it is pretty simple.
1. Add the Fonits WYSIWYG Editor Extension (free) – http://www.magentocommerce.com/magento-connect/fontis-wysiwyg-editor.html
2. Add the transactional emails text editor Text Area CSS ID value in “System” > “Configuration” > “Admin” > WYSIWYG Editor – the value is template_text
3. Save the config
You should how have WYSIWYG editing ability in transactional emails.
NOTE: You can also watch this Video for this info – http://vimeo.com/4316043
Does it work for you?