config.jsonc

{
    "userjs": {
        // This keeps the existing defaults (found in modules/userjs/index.json)
        // enabled As of the time of writing current defaults include disable
        // telemetry, studies and mozilla promotions
        "extend": ["blockImplicitOutbound.js", "disableCaptivePortal.js", "disablePasswords.js"]
    },
    // This same .extend can be applied to anywhere you can use .enabled. The
    // .enabled property sets what is enabled (without defaults included) and
    // .extend extends those defaults. When using the CLI tool .enabled is
    // generated but defaults are pre-selected
    "css": {
        // Add sliding bookmarks menu, leave defaults of ublock icon change,
        // privacy email text, etc
        "extend": ["sliding-bookmarks-menu.css"]
    }
}