let
  Source = {"B", "F", "T"}, 
  AllCombinations = List.Transform(
    {1 .. (Number.Power(2, List.Count(Source)) - 1)}, 
    (number) =>
      List.Select(
        List.Transform(
          List.Positions(Source), 
          (pos) =>
            if Number.BitwiseAnd(number, Number.Power(2, pos)) <> 0 then Source{pos} else null
        ), 
        (value) => value <> null
      )
  ), 
  AllCombinationsAsText = List.Transform(AllCombinations, Text.Combine)
in
  AllCombinationsAsText