You could use a macro in the document template (or in the document if saved as macro enabled, but not the normal template or it will apply to all tables) to add two rows and format them as you tab out of the last cell.
Code:
Sub NextCell()
'Graham Mayor - https://www.gmayor.com - Last updated - 31 Mar 2021
Dim oTable As Table
Dim iCol As Integer, iRow As Integer
Dim lngLast As Long
Set oTable = Selection.Tables(1)
With oTable
iCol = .Columns.Count
iRow = .Rows.Count
If Selection.InRange(.Cell(iRow, iCol).Range) Then
lngLast = Val(.Cell(iRow, 1).Range.Text)
.Rows(iRow).Range.Rows.Add
.Rows(iRow).Range.Rows.Add
.Rows(iRow + 1).Shading.BackgroundPatternColor = RGB(234, 244, 246)
.Rows(iRow + 2).Shading.BackgroundPatternColor = wdColorAutomatic
.Rows(iRow + 2).Cells(1).Range.Text = lngLast + 1
.Rows(iRow + 2).Cells(2).Range.Select
'.Rows(iRow + 2).Range.Style = "Form Body"
Selection.Collapse 1
Else
Selection.Cells(1).Next.Range.Select
Selection.Collapse 1
End If
End With
lbl_Exit:
Set oTable = Nothing
Exit Sub
End Sub