Change column names based on a condition

Hi,

GIVEN

WHEN

let
    Source = Excel.CurrentWorkbook(){[Name="Table1"]}[Content], // YOUR table here
    #"Unpivoted Other Columns" = Table.UnpivotOtherColumns(Source, {"Merged.1"}, "Attribute", "Value"),
    #"Added Index" = Table.AddIndexColumn(#"Unpivoted Other Columns", "Index", 0, 1, Int64.Type),
    #"Added Custom" = Table.AddColumn(#"Added Index", "LevelColumnName", each if Text.StartsWith([Value], "L") then [Index] else null),
    OriginalLevelIndices = List.RemoveNulls(Table.Column(#"Added Custom", "LevelColumnName")),
    NewLevelIndices = List.Numbers(1, List.Count(OriginalLevelIndices)),
    TranslationTable = Table.FromColumns({NewLevelIndices,OriginalLevelIndices}),
    Final = List.Accumulate(Table.ToRows(TranslationTable), #"Added Custom", (t,r) => Table.ReplaceValue(t, r{1}, r{0}, Replacer.ReplaceValue, Table.ColumnNames(t))),
    #"Added Custom1" = Table.AddColumn(Final, "NewColumnNames", each if [LevelColumnName] <> null then "Level" & Text.From([LevelColumnName]) else [Attribute]),
    #"Removed Columns" = Table.RemoveColumns(#"Added Custom1",{"Attribute", "Index", "LevelColumnName"}),
    #"Pivoted Column" = Table.Pivot(#"Removed Columns", List.Distinct(#"Removed Columns"[NewColumnNames]), "NewColumnNames", "Value")
in
    #"Pivoted Column"

THEN the "level" columns should be renamed

Hope this helps.