Here is a mod, which is not an extension of the game, but is intended as a help for the admins/modders among you.
It does nothing else than display all icons of the game.
To open the window just type the command ‘xui open ui_game_symbols’.
Have fun with it.
Dwarfmaster1974 just added the missing icons and also the name of the icon. This makes the whole thing a little more usable.
The forum topic of the mod is here.