Insert a custom row

let
Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMs3NVYrViVYyh9KGBnCGtgKMaQpnaENZRgZwBlzIFM6ACRkbwBlwIVM4AyZkYgBnwISci/LL88Asp8zikqJ8MDMgJ7EkFcwKLknMS0ksSgFzfBKL0oHCsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t]),
#"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}}),
#"Renamed Columns" = Table.RenameColumns(#"Changed Type",{{"Column1", "Sizes"}}),
#"Added Index" = Table.AddIndexColumn(#"Renamed Columns", "Index", 0, 1, Int64.Type),
Custom1 = Table.TransformColumns(#"Added Index",{"Sizes",each let a=Text.Split(_,"+") in a{0}&Text.Trim(a{1}?)&"+"??_}),
Custom2 = Custom1 &#table(Table.ColumnNames(Custom1),{{"export",Table.RowCount(Custom1)}})
in
Custom2