Content of docked blocks are not accessible to screen readers. There is no prompt highlighting expandable items.

When a block is docked, screen reader users cannot access the contents of the block. Technically, it is possible for a screen reader user to access the contents of a docked block if the user knows exactly how the page is laid out, but Moodle does not give any indications or clues as to how to access the block's contents. Blocks must be undocked for the screen reader users to effectively access them.

Potential Solution:
Use ARIA to denote that it is a menu with an expandable submenu