modules/ckeditor5/css/toolbar.admin.css
.ckeditor5-toolbar-disabled {
  display: flex;
  justify-content: space-between;
}
.ckeditor5-toolbar-available {
  flex: 1;
}

.ckeditor5-toolbar-tray {
  display: flex;
  flex-flow: row wrap;
  align-items: center;
  min-height: 40px;
  margin: 0 0 0.5em 0;
  padding: 0;
  list-style: none;
  /* Disallow any user selections in the drag-and-drop toolbar config UI. */
  user-select: none;
}

.ckeditor5-toolbar-active__buttons {
  margin: 5px 0;
  padding: 0.1667em 0.1667em 0.08em;
  border: 1px solid #c4c4c4;
  border-radius: 2px;
  background: #fafafa;
}

.ckeditor5-toolbar-item,
.ckeditor5-toolbar-button {
  display: block;
  min-width: 36px;
  height: 36px;
  cursor: move;
  border-radius: 2px;
}

.ckeditor5-toolbar-item {
  position: relative;
  margin: 5px 8px 5px 0;
}

.ckeditor5-toolbar-disabled .ckeditor5-toolbar-item {
  border: 1px solid #e6e6e6;
}

.ckeditor5-toolbar-button {
  border: none;
  background-color: #eee;
  background-repeat: no-repeat;
  background-position: center;
  background-size: 20px;
}

.ckeditor5-toolbar-button:focus,
.ckeditor5-toolbar-button:hover {
  color: #000;
  background-color: #e6e6e6;
}

.ckeditor5-toolbar-button:focus,
.ckeditor5-toolbar-button:hover,
.ckeditor5-toolbar-button {
  text-decoration: none;
}
.ckeditor5-toolbar-tooltip {
  position: absolute;
  z-index: 1;
  left: 50%;
  display: block;
  padding: 6px 10px;
  transform: translate(-50%, 2px);
  text-transform: capitalize;
  color: #fff;
  border-radius: 3px;
  background: #333;
  font-size: 12px;
  line-height: 1;
}

.ckeditor5-toolbar-tooltip::before {
  position: absolute;
  top: -10px;
  left: 50%;
  width: 0;
  height: 5px;
  content: "";
  transform: translateX(-50%);
  border-right: solid 5px transparent;
  border-bottom: solid 5px #333;
  border-left: solid 5px transparent;
}

.ckeditor5-toolbar-button + .ckeditor5-toolbar-tooltip {
  visibility: hidden;
}
.ckeditor5-toolbar-button[data-expanded="true"] + .ckeditor5-toolbar-tooltip {
  visibility: visible;
}
