Epression.Evaluate in combination with Text.Combine

And here is a modification using a list of columns as an additional argument:

(myTable as table, mergCols as list) => 
    let        
        #"Inserted Merged Column" = Table.AddColumn(myTable, "Merged", (r)=>
            Text.Combine(
                List.Transform(
                    Record.FieldValues(
                        Record.SelectFields(
                            r,mergCols)), 
                    each Text.From(_,"en-BE"))
                ," | "), type text),

        Result= #"Inserted Merged Column" 
    in
        Result

If you named this : fn-CombineCols, you could call it like this in your main query:

    #"Added HASH" = #"fn-CombineCols"(#"Changed Type",
       {
        "Capakey", 
        "Partnumber", 
        "Name", 
        "Street", 
        "Number", 
        "Postcode", 
        "Location", 
        "Province", 
        "StartDate", 
        "EndDate"
       })

Examining your existing code more closely, you have already type all of the columns as text. That being the case, you can remove from the function the List.Transform(...) and shorten to:

(myTable as table, mergCols as list) => 
    let        
        #"Inserted Merged Column" = Table.AddColumn(myTable, "Merged", (r)=>
            Text.Combine(
                    Record.FieldValues(
                        Record.SelectFields(
                            r,mergCols))
                ," | "), type text),

        Result= #"Inserted Merged Column" 
    in
        Result