data = Import[#, "Data"] & /@ filesall;
files = FileNames["*.dat"];
legend = StringReplace[files, ".dat" -> ""];

plot1 = ListLinePlot[data[[1]], PlotLegends -> legendcfinal[[1]]];
plot2 = ListLinePlot[data[[2]], PlotLegends -> legendcfinal[[2]]];

Manipulate[
Show[
  If[x1 == True, plotall, Sequence @@ {}],
  If[x2 == True, plotf1, Sequence @@ {}],
  {{x1, True, "plot1"}, {True, False}}, {{x2, True, "plot2"}]