Creating a New Table with Specific Columns Values From an Existing Table

Eoekid 

Pls see if this is what you want

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUXKMN4wvS8wBs4zgLGMoywku6wSXdYLKxupEKxlRZkIsAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, A_1 = _t, A_2 = _t, A_3 = _t, B_1 = _t, B_2 = _t, B_3 = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"A_1", type text}, {"A_2", type text}, {"A_3", type text}, {"B_1", type text}, {"B_2", type text}, {"B_3", type text}}),
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(#"Changed Type", {"ID"}, "Attribute", "Value"),
    #"Duplicated Column" = Table.DuplicateColumn(#"Unpivoted Other Columns", "Attribute", "Attribute - Copy"),
    #"Extracted Last Characters" = Table.TransformColumns(#"Duplicated Column", {{"Attribute", each Text.End(_, 1), type text}}),
    #"Extracted First Characters" = Table.TransformColumns(#"Extracted Last Characters", {{"Attribute - Copy", each Text.Start(_, 1), type text}}),
    #"Replaced Value" = Table.ReplaceValue(#"Extracted First Characters","1","W",Replacer.ReplaceText,{"Attribute"}),
    #"Replaced Value1" = Table.ReplaceValue(#"Replaced Value","2","X",Replacer.ReplaceText,{"Attribute"}),
    #"Replaced Value2" = Table.ReplaceValue(#"Replaced Value1","3","Y",Replacer.ReplaceText,{"Attribute"}),
    #"Pivoted Column" = Table.Pivot(#"Replaced Value2", List.Distinct(#"Replaced Value2"[Attribute]), "Attribute", "Value"),
    #"Renamed Columns" = Table.RenameColumns(#"Pivoted Column",{{"Attribute - Copy", "Z"}})
in
    #"Renamed Columns"