discourse/app/assets/stylesheets/common/select-kit/user-notifications-dropdown.scss

.select-kit {
  &.dropdown-select-box {
    &.user-notifications-dropdown {
      text-align: left;

      .d-icon {
        margin-left: 0;
      }

      .select-kit-body {
        width: 485px;
        max-width: 485px;
      }

      .select-kit-header {
        justify-content: center;
      }

      .dropdown-select-box-header {
        align-items: center;
      }
    }
  }
}