onSubmit(i:number) {
  console.log('editing '+i+' new val:'+this.editval);
  if(this.editval.length>0)
    this.strtransforms[i]=this.editval; //update cell
  else
    alert('cant add empty transform')

    console.log('transforms: '+JSON.stringify(this.strtransforms))
    this.strtransforms.push("click me")
    console.log('transforms: '+JSON.stringify(this.strtransforms))
 }

<div *ngIf="!loading$">
        <div cdkDropList class="example-list" (cdkDropListDropped)="drop($event)">
                <div class="example-box" *ngFor="let s of strtransforms;index as i" cdkDrag
                        [contentEditable]="true" (contextmenu)="rclick(i)"
                        (input)="editval = $event.target.innerText">{{s}}
                        <fa-icon [icon]="['fas', 'coffee']" (click)="onSubmit(i)"></fa-icon>
                </div>
        </div>
</div>