Creating a column to help pivot data

RichardP  Please try this in Power Query Editor

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjAwMFTSUQpKTVFwys/PBjINlWJ1wOJGQI5TTmkqTMIIWcK9KDU1DyZjDJMxRtNiApMwAXIiU3Ny8sthUqbIUgGlRQU5cF1myFIoFpkjyyBbZKEUGwsA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type text) meta [Serialized.Text = true]) in type table [#"Order No" = _t, LineItem = _t, Index = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Order No", Int64.Type}, {"LineItem", type text}, {"Index", Int64.Type}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Order No"}, {{"AllRows", each _, type table}}),
    #"Added Custom" = Table.AddColumn(#"Grouped Rows", "LineItem", each [AllRows][LineItem]),
    #"Extracted Values" = Table.TransformColumns(#"Added Custom", {"LineItem", each Text.Combine(List.Transform(_, Text.From), ","), type text}),
    #"Split Column by Delimiter" = Table.SplitColumn(#"Extracted Values", "LineItem", Splitter.SplitTextByDelimiter(",", QuoteStyle.Csv), {"LineItem.1", "LineItem.2", "LineItem.3", "LineItem.4"}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Split Column by Delimiter",{{"LineItem.1", type text}, {"LineItem.2", type text}, {"LineItem.3", type text}, {"LineItem.4", type text}}),
    #"Removed Columns" = Table.RemoveColumns(#"Changed Type1",{"AllRows"})
in
    #"Removed Columns"

For Reference, Here is the overview of the steps that are implemented as above.