discourse/app/assets/stylesheets/common/form-kit/_control-menu.scss

.form-kit__control-menu {
  @include default-input;
  justify-content: space-between;
}

.fk-d-menu {
  .dropdown-menu {
    min-width: 200px;
  }
  .dropdown-menu__item {
    &:hover {
      background: var(--d-hover);
    }
  }
}