Hello!
When Expand code blocks by default is set:

When Expand code blocks by default is not set:

Code block expand-collapse icon should also be there when Expand code blocks by default is not set which then can be used to expand the code block.
Version information
- Platform: web (in-browser)
For the web app:
- Browser: Firefox 90.0 (64-bit)
- OS: Ubuntu 20.04.2 LTS
- URL: app.element.io