discourse/plugins/chat/assets/stylesheets/common/chat-modal-archive-channel.scss

.chat-modal-archive-channel {
  .chat-to-topic-selector {
    width: auto;
    height: 300px;
  }

  .radios {
    margin-bottom: 10px;
    display: flex;
    flex-direction: row;

    .radio-label {
      margin-right: 10px;
    }
  }

  details {
    margin-bottom: 9px;
  }

  input[type="text"],
  .select-kit.combo-box.category-chooser {
    width: 100%;
  }
}