Faster Division/Multiplication using Merge same table Query - Power Query

It's not clear why you don't want to do row-level transformations.
Nothing comes to mind about how to use the Table.Join functions to do these transformations (considering that these functions do not expose parameters which are functions that act on the rows / columns of the tables). You should provide the exact references of the post where you found these tips.
In the meantime, I can offer you this "strange" solution that makes use of the pivot and unpivot functions.

let
    Origine = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("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", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, CD = _t, #"6" = _t, #"5" = _t, #"4" = _t, #"3" = _t, #"1" = _t, Count = _t]),
    #"Rimosse colonne" = Table.RemoveColumns(Origine,{"ID","Count"}),
    #"Modificato tipo" = Table.TransformColumnTypes(#"Rimosse colonne",{{"6", Int64.Type}, {"5", Int64.Type}, {"4", Int64.Type}, {"3", Int64.Type}, {"1", Int64.Type}}),
    #"Trasformate altre colonne tramite UnPivot" = Table.UnpivotOtherColumns(#"Modificato tipo", {"CD"}, "Attributo", "Valore"),
    #"Rimosse colonne1" = Table.RemoveColumns(#"Trasformate altre colonne tramite UnPivot",{"Attributo"}),
    #"Colonna trasformata tramite Pivot" = Table.Pivot(#"Rimosse colonne1", List.Distinct(#"Rimosse colonne1"[CD]), "CD", "Valore", (v)=>List.Transform(v, each _/List.Sum(v))),
    #"Trasposta colonna" = Table.Transpose(#"Colonna trasformata tramite Pivot"),
    #"Valori estratti" = Table.TransformColumns(#"Trasposta colonna", {"Column1", each Text.Combine(List.Transform(_, Text.From), ":"), type text}),
    #"Suddividi colonna in base al delimitatore" = Table.SplitColumn(#"Valori estratti", "Column1", Splitter.SplitTextByDelimiter(":", QuoteStyle.Csv), {"Column1.1", "Column1.2", "Column1.3", "Column1.4", "Column1.5"}),
    #"Modificato tipo1" = Table.TransformColumnTypes(#"Suddividi colonna in base al delimitatore",{{"Column1.1", type number}, {"Column1.2", type number}, {"Column1.3", type number}, {"Column1.4", type number}, {"Column1.5", type number}})
in
    #"Modificato tipo1"

Hi Anonymous - oddly enough I do not think you can reference another column within a Table.TransformColumn. I've not see a way to do it.

However, you can use the Table.ReplaceValue function. See below - this is just for column 6. You'd need to repeat for each column.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("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", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [DI = _t, CD = _t, #"6" = _t, #"5" = _t, #"4" = _t, #"3" = _t, #"1" = _t, Count = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"6", Int64.Type}, {"5", Int64.Type}, {"4", Int64.Type}, {"3", Int64.Type}, {"1", Int64.Type}, {"Count", Int64.Type}}),
    #"Replaced Value" = 
    Table.ReplaceValue(
        #"Changed Type",
        each
        let
            varCurrentValue = [6]
        in
            varCurrentValue,

            each [6] / [Count],
            Replacer.ReplaceValue,{"6"})
in
    #"Replaced Value"

Here is what it does:

• It assigns the current value of column 6 to the varCurrentValue variable. (current value is whatever it is for each row)
• It searches for the current value.
• Then it replaces it with [6] / [Count]

I did test this with 2 records that had the same value (45) but different values in the Count column for that row, and it worked.

The first value was 45, and now divided by 302 gives the .149 value.

How to use M code provided in a blank query:
1) In Power Query, select New Source, then Blank Query
2) On the Home ribbon, select "Advanced Editor" button
3) Remove everything you see, then paste the M code I've given you in that box.
4) Press Done
5) See this article if you need help using this M code in your model.

Have you tried just transforming the columns?

Table.TransformColumns(PriorStep, {{"6",each _/[Count]}, {"5", each _/[Count]}})

No reason that shouldn't work for ya.