override getQuickFilters() like this..

protected getQuickFilters(): Serenity.QuickFilter<Serenity.Widget, any>[] {

let filters = super.getQuickFilters();
        let fld = Welfare.DaughterMarriageGrantRow.Fields;
        let filter = Q.first(filters, x => x.field == fld.EmpName);
        filter.title = "Applicant Name";
        filter.type = Serenity.StringEditor;
        filter.handler = h => {
            if (h.active) {
                h.request.Criteria = Serenity.Criteria.and(h.request.Criteria,
                    [[fld.EmpName], 'like', '%' + h.value + '%']);
            }
        };
        return filters;
    }