How can I split a column of data into 2 columns, based on the value of another column

You can use the Table.Group function. The code below assumes that there is one or two customers per Product. If there might be more, the code can be rewritten to handle any number of customers.

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMjQAAiUdJVMDpVgdJK4hnGsI4hrBuUYgrjEq1wTONQZxTVG5ZnCuCSrXFNUoU6hRsQA=", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [#"Product Num..." = _t, #"Customer Nu..." = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Product Num...", Int64.Type}, {"Customer Nu...", Int64.Type}}),
    
    #"Grouped Rows" = Table.Group(#"Changed Type", {"Product Num..."}, {
        {"Customer 1", each [#"Customer Nu..."]{0}, type nullable text},
        {"Customer 2", each try [#"Customer Nu..."]{1} otherwise null, type nullable text}
    })
in
    #"Grouped Rows"

Thank you so much. I can pretend to understand at first glance but I'll be delving into your suggestion. Thanks again