Power Query: Adding a helper column for comparing multiple rows

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("hdG9CsIwEMDxVymZhdxX0ms2X8ChjqWL4OAgFlGf37SIaWokW4Yff+4uw2D6Xg8MwCyeyezM8Xm6Xh7xQa1FtAREDVBgNOPuV++n6X57nWeuiXdBOOMiXtt1HDoLi+YGJaAUdYrnnLASJwv60RCorcVzrttF4y7ls8yai/rfWTaLFniX6i4Q5NyTy2ZB+E4OGoSKOsXXPM5Si2dnQVeLc+LxR7XGXeJ+mWV8Aw==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Requisition Number" = _t, #"Action Code" = _t, #"Action Date" = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Requisition Number", type text}, {"Action Code", type text}, {"Action Date", type datetime}},"en-GB"),
    #"Sorted Rows" = Table.Sort(#"Changed Type",{{"Requisition Number", Order.Ascending}, {"Action Date", Order.Ascending}}),
    #"Grouped Rows" = Table.Group(#"Sorted Rows", {"Requisition Number", "Action Code"}, {{"Rows", each _, type table [Requisition Number=nullable text, Action Code=nullable text, Action Date=nullable datetime]}, {"Helper Column", each Table.RowCount(_), Int64.Type}},GroupKind.Local),
    #"Expanded Rows" = Table.ExpandTableColumn(#"Grouped Rows", "Rows", {"Action Date"}, {"Action Date"}),
    #"Replaced Value" = Table.ReplaceValue(#"Expanded Rows",each [Helper Column],each if [Helper Column]=1 then "No" else "Yes",Replacer.ReplaceValue,{"Helper Column"}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Replaced Value",{{"Helper Column", type text}})
in
    #"Changed Type1"

How to use this code: Create a new Blank Query. Click on "Advanced Editor". Replace the code in the window with the code provided here. Click "Done".