Minecraft wiki entry for Development_versions, associated text: Added a new "accessibility menu".
All accessibility features are now easily toggled in this menu.
When the narrator is turned on, buttons will be narrated on focus.
Added a new option that allows turning up transparent backgrounds.
Menu buttons, edit boxes and other UI elements can now be cycled through by pressing Tab ↹.
⇧ Shift + Tab ↹ will go backwards.
Lists allow ↑ and ↓ arrow keys to navigate through them.