如果mat-table超出屏幕长度并显示，则隐藏额外的列，然后单击将放置在其旁边的+按钮

ng add @angular/material

import { MatTableModule } from '@angular/material/table';
import { MatButtonModule } from '@angular/material/button';

@NgModule({
  imports: [
    MatTableModule,
    MatButtonModule
  ],
  ...
})

<mat-table [dataSource]="dataSource">
  <ng-container matColumnDef="column1">
    <mat-header-cell *matHeaderCellDef> Column 1 </mat-header-cell>
    <mat-cell *matCellDef="let element"> {{element.column1}} </mat-cell>
  </ng-container>

  <ng-container matColumnDef="column2">
    <mat-header-cell *matHeaderCellDef> Column 2 </mat-header-cell>
    <mat-cell *matCellDef="let element"> {{element.column2}} </mat-cell>
  </ng-container>

  <!-- 添加更多的列 -->

  <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
  <mat-row *matRowDef="let row; columns: displayedColumns;"></mat-row>
</mat-table>

@media (max-width: 600px) {
  .hide-column {
    display: none;
  }
}

<button mat-raised-button (click)="addRow()">+</button>

addRow() {
  // 向数据源中添加一行数据
  this.dataSource.push({ column1: 'New Data', column2: 'New Data' });
}