Dropdown Icons
:icon: draws a GitHub octicon before the title. The name is checked while
parsing, so a misspelled one is reported as dropdown.unknown-icon rather
than silently drawing nothing.
A hint
:icon: light-bulb, the icon the sphinx-needs demo uses for its own
hints.
An experiment
:icon: beaker
A warning sign
:icon: alert
An icon combines with everything else, including a title carrying its own markup:
Reading conf.py
The icon sits before the title text; the state marker stays on the right.