There is a workaround.
- Install the glossary_random block. Normally it is used to display random entries from the glossary. If you only add one entry, it always displays this one. That's why it could be used to just display a course description.
- Add a glossary to your course and (optional) hide it from students
- Add just one entry to the glossary. Write the text you want to display. If you are using the HTML editor, you can also include pictures.
- After adding the block to a course, a link shows up: change settings for this block.
- Clicking on the link takes you to a page where you can change the title to something like 'Course description'
- Make sure you select the glossary you created in step 2.