How to add one more heading which should be located after after the name of the columns but before the data array? In general, I want to do something like this.

I tried to add just an empty header but it does not appear:

<th mat-header-cell *matHeaderCellDef></th>


html:

<table mat-table [dataSource]="dataSource" matSort matSortDisableClear matSortActive="NAME"
matSortDirection="asc">
<ng-container [matColumnDef]="column.value" *ngFor="let column of allCols;">
{{column.displayName}}
</th>
<td mat-cell *matCellDef="let row">
{{row[column.lowercaseValue]}}
</td>
</ng-container>
<ng-container matColumnDef="button">