wagtail/client/scss/layouts/_groups-edit.scss

.listing {
  .field label {
    @include visuallyhidden;
  }

  input,
  select,
  textarea {
    font-size: 1em;
  }

  select + span:after {
    // stylelint-disable-next-line declaration-no-important
    font-size: 2.5em !important;
  }

  .custom-permissions {
    padding-bottom: 0;
  }

  .custom-permissions-item {
    font-weight: inherit;
    width: 100%;
    padding: 0;
  }
}

.page-permissions-listing {
  .admin_page_chooser .field-content {
    width: 100%; // so that 'choose another page' button displays in its entirety
  }
}