How to set multiple selection in dropdown in ng2-smart-table?

I think you can try with your own custom editor component. I've added a basic select with a multiple attribute, but you can create a custom component more complex as you prefer.

Pass data to your component with valuePrepareFunction and voila.

settings.ts

private settings = {
 // Previous config ...

 columns: {
  multiple: {
    title: 'Multi select',
    type: 'html',
     editor: {
      type: 'custom',
      valuePrepareFunction: (cell, row) => row,
      component: MultiSelComponent,
     },
  }
 }
}

multiSel.component.html

<select multiple [(ngModel)]="yourModelStore">
  <option *ngFor="let item of myValues" [value]="item.value">{{item.name}}</option>
</select>

multiSel.component.ts

import { Component, Input, OnInit } from '@angular/core';
import { ViewCell } from 'ng2-smart-table';

....

export class MultiSelComponent implements OnInit {

  @Input() value;

  yourModelStore: any; // rendered as this.yourModelStore = ['value', 'value'];

  ngOnInit() {
    this.myValues = this.value;
  }

module.ts

declarations:[
  //others ...

  MultiSelComponent
]
entryComponents: [
  MultiSelComponent
]

**I've edit the answer and added more infos on setting and component.ts