Summary under subtotal

Hi carsoncheng, it is not ideal but possible also in PowerQuery:

Output

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WclTSUTIEYicDIAAxDA2UYnXQxI2ADCOEuBFM3BjEMYWLg7i+MHOMIeqdMMw3hYsboZsfCwA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Faculty = _t, Year = _t, #"Program code" = _t, Quota = _t]),
    ChangedType = Table.TransformColumnTypes(Source,{{"Year", Int64.Type}, {"Quota", type number}}),
    GroupedRows = Table.Group(ChangedType, {"Faculty"}, {{"T", each 
        [ A = _,
        //   A = GroupedRows{[Faculty="A"]}[T],
          SelectedCols = Table.Buffer(Table.SelectColumns(A,{"Year", "Quota"})),
          Ad_Totals = List.Accumulate(let lst = List.Distinct(SelectedCols[Year]) in lst & {lst} , A, (s,c)=>
                if c is number then Table.InsertRows(s, Table.RowCount(s), { SelectedCols{0} & [Faculty=if c = SelectedCols{0}[Year] then "By-year" else null, Year=c, Program code=null, Quota=List.Sum(Table.SelectRows(SelectedCols, each [Year] = c)[Quota])] })
                else Table.InsertRows(s, Table.RowCount(s), { SelectedCols{0} & [Faculty=null, Year="Total", Program code=null, Quota=List.Sum(Table.SelectRows(SelectedCols, each List.Contains(c, [Year]))[Quota])] })),
          Ad_SpaceRow = Table.InsertRows(Ad_Totals, Table.RowCount(Ad_Totals), { List.Accumulate(Table.ColumnNames(Ad_Totals), [], (s,c)=> Record.AddField(s, c, null)) } )
        ][Ad_SpaceRow], type table}}),
    CombinedT = Table.Combine(GroupedRows[T]),
    SelectedCols2 = Table.Buffer(Table.SelectRows(CombinedT, each [Program code] = null and [Year] <> null)[[Year], [Quota]]),
    Ad_Total = List.Accumulate(List.RemoveNulls(List.Distinct(SelectedCols2[Year])), CombinedT, (s,c)=>
                Table.InsertRows(s, Table.RowCount(s), { SelectedCols2{0} & [Faculty=if c = SelectedCols2{0}[Year] then "All" else null, Year=c, Program code=null, Quota=List.Sum(Table.SelectRows(SelectedCols2, each [Year] = c)[Quota])] }))

in
    Ad_Total