Actually those available bbcode tag already listed into that editor page, you can check my attached screenshot below.
BBCode is 3rd party anyway, so what is the difficulty to get it work?
Currently we haven't plan to add this yet, but you can submit a feature request regarding this on our forum here
https://stackideas.com/forums/easydiscuss/feature-requests .We will prioritize this feature during the development process for the next major version of EasyDiscuss if there are more people request on this.