editor.js/src/styles/toolbar.css

.ce-toolbar {
  position: absolute;
  left: 0;
  right: 0;
  top: 0;
  /*opacity: 0;*/
  /*visibility: hidden;*/
  transition: opacity 100ms ease;
  will-change: opacity, transform;
  display: none;

  @media (--mobile) {
    @apply --overlay-pane;
    padding: 3px;
    margin-top: 5px;
  }

  &--opened {
    display: block;

    @media (--mobile){
      display: flex;
    }
  }

  &__content {
    max-width: var(--content-width);
    margin: 0 auto;
    position: relative;

    @media (--mobile){
      display: flex;
      align-content: center;
      margin: 0;
      max-width: calc(100% - 40px);
    }
  }

  &__plus {
    @apply --toolbox-button;

    position: absolute;
    left: calc(var(--toolbox-buttons-size) * -1);
    flex-shrink: 0;

    &--hidden {
      display: none;
    }

    @media (--mobile){
      display: inline-flex !important;
      position: static;
      transform: none !important;
    }
  }

  &__plus,
  .ce-toolbox {
    top: 50%;
    transform: translateY(-50%);
  }

  /**
   * Block actions Zone
   * -------------------------
   */
  &__actions {
    position: absolute;
    right: 0;
    top: 10px;
    padding-right: 16px;
    opacity: 0;

    @media (--mobile){
      position: static;
      margin-left: auto;
      padding-right: 10px;
      display: flex;
      align-items: center;
    }

    &--opened {
      opacity: 1;
    }

    &-buttons {
      text-align: right;
    }
  }

  &__settings-btn {
    display: inline-block;
    width: 24px;
    height: 24px;
    color: var(--grayText);
    cursor: pointer;
  }
}

/**
 * Styles for Narrow mode
 */
.codex-editor--narrow .ce-toolbar__plus {
  @media (--not-mobile) {
    left: 5px;
  }
}