I wanted to share a discovery with the CK: http://img.photobucket.com/albums/v519/Cliffworms/SoSVolumeSliders.jpg
In the Audio/Sound Category section (Object View), you have to create your own Sound Category and check the "Should appear on Menu" option. If it's an ambient sound effect, I recommend choosing the "AudioCategoryPausedDuringMenuFade" Parent in the selection box. This will make the sounds linked to it behave like most vanilla sound effects and fade out when the player is in a menu.
To link sound effects to the category you created, in your Sound Descriptor's properties, you have to select the Sound Category you created.
In-game, your own audio setting is then added to the selected sound effects. Very neat feature. The setting's name is smaller or bigger depending on its name's length, creating uneven font sizes between settings, but that's not an issue.
Doing it this way also links your sound category to the "Effects" and "Master" settings since its parent's parent's parent's (etc) eventually leads to "Master". So if the player mutes "Master" or "Effects", your sound categories also get muted.
You can assign them to be their own Master by not choosing a Parent. The drawback is that the sounds play if the player is in a menu (Those presets seem to be hardcoded)
The Creation Kit gives an error when loading mods with too many Menu Sound Categories, but seems like clicking on "Retry" makes the CK works anyway. Adding custom sliders from different loaded esps will show up correctly in the Audio settings too. I have added around 30-35 volume sliders and didn't run into any issues.
I'm using custom volume sliders for Sounds of Skyrim to allow the player to adjust the sounds' volume to their taste or mute them. This can be very useful for anyone adding new custom sound effects and saves the time to create a scripted menu to do this work.
I hope you enjoy this new discovery as much as I did.