Extracting Values From a List & Inserting in Table at Specific Rows

Hello Andyb431 

try this approach. Use your BenefitGUID-table and add a new column where you inserting you Timeline-table on every row. After that you expand the table

let
    Base_AnalysisTimeline=
    let
        Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlSK1YlWMgKTxmDSBEyagkkzMGkOJi2UYmMB", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Count = _t]),
        #"Changed Type" = Table.TransformColumnTypes(Source,{{"Count", Int64.Type}})
    in
        #"Changed Type",
    
    BenefitGUID = #table({"Benefit GUID"}, {{"U1B1"}, {"U1B2"}, {"U1B3"}}),

    Multiply = Table.AddColumn
    (
        BenefitGUID,
        "BaseAnalysisTimeLine",
        each Base_AnalysisTimeline
    ),
    Expand = Table.ExpandTableColumn(Multiply, "BaseAnalysisTimeLine", {"Count"}, {"Count"})
in  
    Expand

Copy paste this code to the advanced editor in a new blank query to see how the solution works.

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Kudoes are nice too

Have fun

Jimmy