How to Mute a Specific Annoying Sound (Like the Nether Portal) in the Sound Controller Mod
Opening the Individual Sounds Screen
Open your pause menu and go to Options → Music & Sounds. At the bottom of that screen you'll find a new button labeled Individual Sounds. Click it to open the Sound Controller configuration screen, which lists every sound the game and your installed mods register.
Finding and Silencing the Sound
Use the search bar at the top of the screen to filter the list. Sound names are technical, so try typing a keyword that matches the source — for example, typing portal narrows the list to portal-related entries, and enderman narrows it to Enderman sounds. Once you spot the entry you want, drag its volume slider all the way down to zero to mute it, or set it to a lower value if you only want to reduce it.
Verifying and Keeping Changes
Trigger the sound in-game to confirm it's now silent or quieter. If you muted the wrong entry, drag the slider back up. Your changes are saved by the mod, so they persist between sessions. If you later want to review everything you've touched, use the toggle that filters the list down to only your modified volumes — that way you don't have to remember which entries you changed.