How do I add a row in Employee Timecard via BLC code?

I have code that uses the RowInserted event to update specific fields in a newly added grid row for the Employee Timecard screen (EP305000) Details section when the '+' button is pressed. The problem is that after the code updates these fields, I can see in the UI that they've been updated - but when I hit the save button, the row disappears - as if it's not recognized as being added.

Is there a dirty flag that has to be set in order for this additional row to be recognized? If I manually update one of these fields, it then recognizes it and it is added.

Is there something I need to add, like setting a 'dirty flag' to update the grid with this inserted row if purely added through BLC code?

the code:

protected void EPTimecardDetail_RowInserted(PXCache sender, PXRowInsertedEventArgs e)
    {
        string day = null;
        DateTime? date = null;
        DateTime? startDate = null;
        DateTime? endDate = null;
        int? project = null;
        int? task = null;

        if (isCreateCorrectionFlag == false)
        {
            
            //Get the last row's data...
            foreach (EPTimecardDetail tca in Base.Activities.Select())
            {
                if (tca.ProjectID == null) break;  //This is to make sure the variables have the last valid row's data and not the newly inserted row's data
                day = tca.Day;
                date = tca.Date;
                project = tca.ProjectID;
                task = tca.ProjectTaskID;

                var tcae = PXCache<PMTimeActivity>.GetExtension<PMTimeActivityExt>(tca);
                startDate = tcae.UsrStartDate;
                endDate = tcae.UsrEndDate;
            }



            //var tcd = (PMTimeActivity)e.Row;
            var tcd = (EPTimecardDetail)e.Row;
            if (tcd == null) return;

            tcd.Date = date;
            tcd.Day = day;

            var tcde = PXCache<PMTimeActivity>.GetExtension<PMTimeActivityExt>(tcd);
            tcde.UsrStartDate = startDate; //tcd.Date;
            tcde.UsrEndDate = endDate; //tcd.Date;
            tcd.TimeSpent = CalcTimeWorked(tcde);

            tcd.ProjectID = project;
            tcd.ProjectTaskID = task;
            tcd.Summary = "=====";

        }
        //row.BillableTimeCalc = CalcTimeWorked(row);
    }

Per Acumatica support (thanks to them!), the Grid's Mode>AutoInsert property needs to be set to "True". This will allow the grid's auto-inserted row to remain after saving: