Conditional Index M Language - Power Query

Hello DaxBoi 

are you sure that you need some graphical output like your second table? Meaning that your headers are repeating throughout your data? Or should it look like this?

if yes, here the approach to get this result

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45W8khNTMnMS1cwVNJRMjDUByIjAyMYxwjCidWJVnIECoGEjcA8JyDLGIhNwDxnIMsUiM3APJiJRiSZ6IxiIswMYwJmuCDMiAUA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [Column1 = _t, Column2 = _t, Column3 = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Column1", type text}, {"Column2", type text}, {"Column3", type text}}),
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Column1"}, {{"AllRows", each Table.TransformColumnNames(Table.PromoteHeaders(_), (x)=> if Text.StartsWith(x,"Heading") then "Value" else x)}}, GroupKind.Local, (x,y)=> if Text.StartsWith(y[Column1], "Headin") then 1 else 0),
    #"Expanded AllRows" = Table.ExpandTableColumn(#"Grouped Rows", "AllRows", {"Value", "01/01/2021", "01/02/2021"}, {"Value", "01/01/2021", "01/02/2021"})
in
    #"Expanded AllRows"

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