How to move legends to a specific position?

Question

How can I move the legend to the right to left alight with the plot above and move it down a little bit?
Also how can I move it to a specific position below the plot?

colors = ColorData[97] /@ Range[18];
list = {{"a"}, {"b", "c"}, {"d"}, {"e"}, {"f"}, {"g"}, {"h", 
    "k"}, {"l"}, {"m"}, {"n"}, {"p", "q", 
    "k"}, {"x"}, {"y"}, {"z"}, {"kh"}, {"xy"}, {"cy"}, {"cz"}};
linelegend = 
  LineLegend[{Opacity[opacity, Gray], 
    Directive[Red, Thickness[0.01], Dashed], White}, 
   Style[#, 30, Bold, Black] & /@ {"mnk", "htk", "kn"}, 
   "LegendItem" -> {"Square", Automatic, "Square"}, 
   LegendMarkerSize -> 25];
opacity = 0.2;
Dynamic[Legended[
  Row[{Plot[{x^2 - 1, 2 x - 3, 5 - 3 x, 5 x - 2 x^2}, {x, 0, 6}, 
     GridLines -> Automatic, 
     PlotStyle -> 
      ReplacePart[
       Directive[#, Thickness[0.005]] & /@ 
        colors, {Except[Alternatives @@ n]} -> 
        Directive[Opacity[.01], Gray]],
     Ticks -> Automatic,
     Frame -> True,
     Axes -> True,
     PlotStyle -> Thickness[0.5],
     PlotRange -> {{0, 6}, {0, 6}},
     FrameStyle -> Directive[Black, Bold, 20],
     GridLines -> Automatic,
     GridLinesStyle -> LightGray,
     Ticks -> Automatic,
     TicksStyle -> Directive[Black, Bold, 20],
     ImageSize -> 800,
     Epilog -> {Directive[Red, Dashed, Thickness[0.003]], 
       Line[{{0, 1}, {1, 1}, {10, 10}}], Opacity[opacity, Gray], 
       Polygon[{{0, 1}, {1, 1}, {6, 6}, Scaled[{0, 1}, {6, 6}], 
         Scaled[{0, 1}, {0, 1}]}]}], 
    Spacer[10], linelegend}], 
  Placed[TogglerBar[Dynamic[n], 
    MapIndexed[#2[[1]] -> 
       ToString[
         Framed[Style[#2[[1]], Black, Bold, 15], 
          ImageSize -> {45, 45}, Alignment -> Center, 
          Background -> LightBlue], StandardForm] <> 
        ToString[
         Framed[Style[#, colors[[#2[[1]]]], Bold, 15], 
          ImageSize -> {230, 45}, Alignment -> Center, 
          Background -> White], StandardForm] &, list], 
    Appearance -> "Vertical" -> {Automatic, 3}], Below]]]

Answer 1

for example like this:

colors = ColorData[97] /@ Range[18];
list = {{"a"}, {"b", "c"}, {"d"}, {"e"}, {"f"}, {"g"}, {"h", 
    "k"}, {"l"}, {"m"}, {"n"}, {"p", "q", 
    "k"}, {"x"}, {"y"}, {"z"}, {"kh"}, {"xy"}, {"cy"}, {"cz"}};
linelegend = 
  LineLegend[{Opacity[opacity, Gray], 
    Directive[Red, Thickness[0.01], Dashed], White}, 
   Style[#, 30, Bold, Black] & /@ {"mnk", "htk", "kn"}, 
   "LegendItem" -> {"Square", Automatic, "Square"}, 
   LegendMarkerSize -> 25];
opacity = 0.2;
Dynamic[Legended[
  Row[{Plot[{x^2 - 1, 2 x - 3, 5 - 3 x, 5 x - 2 x^2}, {x, 0, 6}, 
     GridLines -> Automatic, 
     PlotStyle -> 
      ReplacePart[
       Directive[#, Thickness[0.005]] & /@ 
        colors, {Except[Alternatives @@ n]} -> 
        Directive[Opacity[.01], Gray]], Ticks -> Automatic, 
     Frame -> True, Axes -> True, PlotStyle -> Thickness[0.5], 
     PlotRange -> {{0, 6}, {0, 6}}, 
     FrameStyle -> Directive[Black, Bold, 20], GridLines -> Automatic,
      GridLinesStyle -> LightGray, Ticks -> Automatic, 
     TicksStyle -> Directive[Black, Bold, 20], ImageSize -> 800, 
     Epilog -> {Directive[Red, Dashed, Thickness[0.003]], 
       Line[{{0, 1}, {1, 1}, {10, 10}}], Opacity[opacity, Gray], 
       Polygon[{{0, 1}, {1, 1}, {6, 6}, Scaled[{0, 1}, {6, 6}], 
         Scaled[{0, 1}, {0, 1}]}]}], Spacer[10], linelegend}],
  
  Placed[{
     Spacer@{0, 80},(* change vertical position here *)
     TogglerBar[Dynamic[n], 
      MapIndexed[#2[[1]] -> 
         ToString[
           Framed[Style[#2[[1]], Black, Bold, 15], 
            ImageSize -> {45, 45}, Alignment -> Center, 
            Background -> LightBlue], StandardForm] <> 
          ToString[
           Framed[Style[#, colors[[#2[[1]]]], Bold, 15], 
            ImageSize -> {230, 45}, Alignment -> Center, 
            Background -> White], StandardForm] &, list], 
      Appearance -> "Vertical" -> {Automatic, 3}]} // Column, {Left, 
    Below} (* second change *)]]]