discourse/plugins/chat/assets/stylesheets/common/chat-index.scss

.channels-list {
  .chat-channel-divider {
    padding: 2.5rem 1.5rem 0.5rem 1.5rem;

    &:first-of-type {
      padding-top: 1rem;
    }
  }

  .chat-channel-title {
    padding-right: 0.5em;
  }
}