Angular CDK Drag & Drop: Don't move source item

replace

drop(event: CdkDragDrop<string[]>) {
  if (event.previousContainer === event.container) {
    moveItemInArray(event.container.data, event.previousIndex, event.currentIndex);
  } else {
    transferArrayItem(
      event.previousContainer.data,
      event.container.data,
      event.previousIndex,
      event.currentIndex
    );
  }
}

with

drop(event: any) {
  if (event.previousContainer === event.container) {
    moveItemInArray(event.container.data, event.previousIndex, event.currentIndex);
  } else {
    copyArrayItem(
      event.previousContainer.data,
      event.container.data,
      event.previousIndex,
      event.currentIndex
    );
  }
}

Import import {copyArrayItem} from '@angular/cdk/drag-drop';

AND

Replace transferArrayItem with copyArrayItem