This icon does not work properly :
If you select “Show Drum Sounds with Events”, it turns on. If you click it, it does not return to “Show All drum sounds”.
Hi,
This is not a toggle button. Once you click it, the drop-down menu appears, and you can select an option you want to. There are more then 2 options.
Hi Martin,
You’re right, it’s not a toggle button, it’s a… come-back-to-show-all-drum-sounds button 
There is a similar button for audio tracks : the Track Visibility Agents button. And this one works fine : when you have selected a visibility option and you click it, it reverts to “All tracks visible” state.
And, by the way, you can see the drop-down menu when you click the arrow next to it, but not when you click it