private void createEditableMarker() {
    TGSongManager songManager =
        this.context.getAttribute(TGDocumentContextAttributes.ATTRIBUTE_SONG_MANAGER);
    TGMarker marker = this.context.getAttribute(TGDocumentContextAttributes.ATTRIBUTE_MARKER);
    if (marker == null) {
      TGMeasureHeader header =
          this.context.getAttribute(TGDocumentContextAttributes.ATTRIBUTE_HEADER);

      marker = songManager.getFactory().newMarker();
      marker.setMeasure(header.getNumber());
    }

    this.marker = marker.clone(songManager.getFactory());
  }