Append Rows using Another columns

This should work:

let
    Source = Excel.CurrentWorkbook(){[Name="Test_Unpivot"]}[Content],
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"Name", type text}, {" Date1 ", type datetime}, {" Cost1 ", type text}, {"Date2", type datetime}, {" Cost2 ", type text}}),
    #"Unpivoted Only Selected Columns" = Table.Unpivot(#"Changed Type", {" Date1 ", " Cost1 ", "Date2", " Cost2 "}, "Attribut", "Value"),
    #"Trimmed Text" = Table.TransformColumns(#"Unpivoted Only Selected Columns",{{"Attribut", Text.Trim, type text}}),
    #"Added Name_temp" = Table.AddColumn(#"Trimmed Text", "Name_temp", each [Name]&Text.End([Attribut],1)),
    #"Replace '1'" = Table.ReplaceValue(#"Added Name_temp","1","",Replacer.ReplaceText,{"Attribut"}),
    #"Replace '2'" = Table.ReplaceValue(#"Replace '1'","2","",Replacer.ReplaceText,{"Attribut"}),
    #"Removed Name" = Table.RemoveColumns(#"Replace '2'",{"Name"}),
    #"Pivoted Column" = Table.Pivot(#"Removed Name", List.Distinct(#"Removed Name"[Attribut]), "Attribut", "Value"),
    #"Add Name" = Table.AddColumn(#"Pivoted Column", "Name", each Text.Start([Name_temp],1)),
    #"Removed Name_temp" = Table.RemoveColumns(#"Add Name",{"Name_temp"}),
    #"Reordered Columns" = Table.ReorderColumns(#"Removed Name_temp",{"Name", "Date", "Cost"}),
    #"Changed Date" = Table.TransformColumnTypes(#"Reordered Columns",{{"Date", type date}})
in
    #"Changed Date"