index.html

<formio-alerts [alerts]="service.alerts"></formio-alerts>
<formio-grid
  [src]="gridSrc"
  [query]="myQuery"
  [onForm]="service.formLoaded"
  (rowSelect)="onSelect($event)"
  (error)="service.onError($event)"
  (createItem)="onCreateItem()"
  [createText]="createText"
></formio-grid>

index.ts

import { Component } from '@angular/core';
import { FormioResourceIndexComponent } from '@formio/angular/resource';

@Component({
  selector: 'app-index',
  templateUrl: './index.html',
  styleUrls: ['./index.scss']
})
export class IndexComponent extends FormioResourceIndexComponent {
  public myQuery = {};
  ngOnInit() {
    super.ngOnInit();
    this.service.formLoaded.then(() => {
      this.service.loadParents().then(() => {
        this.myQuery = this.gridQuery;
        this.myQuery['data.parentId'] = '23423234234234';
      });
    });
  }
}