diagram-js-code-editor/assets/diagram-js-code-editor.css

 .djs-editor {
  position: absolute;
  top: 90px;
  right: 20px;
  /* overflow: hidden; */
  background-color: rgba(255, 255, 255, 0.9);
  border: solid 1px #CCC;
  border-radius: 2px;
  box-sizing: border-box;
  /* user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  -webkit-user-select: none; */
}
.djs-editor:not(.enabled){
  color: #CCC;
  pointer-events: none;
}

.djs-editor.enabled{
  color: rgb(0, 0, 0);
}

.djs-editor:not(.open) {
  overflow: hidden;
}

.djs-editor .ide {
  display: none;
}

.djs-editor.open .ide {
  display: block;
}

.djs-editor .ide {
  width: 620px;
  height: 280px;
}

.djs-editor:not(.open) .toggle {
  width: 46px;
  height: 46px;
  line-height: 46px;
  content: "dvr" !important;
  text-align: center;
}

.djs-editor:not(.open) .toggle:before {
  font-family: "Material Icons", sans-serif;
  content: "dvr" !important;
  font-size: 24px;
}

.djs-editor .toggle:before {
  content: attr(title);
}

.djs-editor.open .toggle {
  position: absolute;
  right: 0;
  padding: 6px;
  z-index: 1;
}