When playing a big mod pack there can be thousands of different particles, making it difficult to find the exact one you want to disable. Some way of searching or filtering (by mod that added it and/or name of the particle) would be greatly appreciated.

As you know Sodium Extra is using Sodium's UI, and it doesn't include a component for textbox(and I don't have the passion to be writing one). So I can recommend using Xander's Sodium Options if you'd like searchable options as it uses vanilla's GUI system.

Implemented in Reese's Sodium Options 1.6.0, which works with Sodium Extra. Add that as well