If anyone has any idea how to turn all of that plotting stuff (hcpii4plot) into a function which takes hcpii4angfunc[\[Theta], \[Phi]] as an argument, that would make my notebook a lot neater and easier to read. I have been struggling with this for a couple of months now and couldn't find how to do it anywhere online...

hcpii4angfunc[\[Theta]_, \[Phi]_] = -1.1619488688971678` + 
  0.8938068222285906` Cos[2 \[Theta]] + 
  3.1283238778000673` Cos[2 \[Theta]]^2

hcpii4plot = 
  SphericalPlot3D[1, {\[Theta], 0, \[Pi]}, {\[Phi], 0, 2 \[Pi]}, 
   ColorFunction -> 
    Function[{x, y, z, \[Theta], \[Phi], r}, 
     ColorData["DarkRainbow"][hcpii4angfunc[\[Theta], \[Phi]]]], 
   ColorFunctionScaling -> False, Mesh -> False, Boxed -> False, 
   AxesOrigin -> {0, 0, 0}, 
   PlotRange -> {{-1.3, 1.3}, {-1.3, 1.3}, {-1.22, 1.22}}, 
   LabelStyle -> Directive[Black, 14], Ticks -> None, 
   AxesStyle -> Arrowheads[{-0.05, 0.05}], 
   Method -> {"ShrinkWrap" -> True}, ViewPoint -> {-2, -2, 1}, 
   ViewVertical -> {1, 1, 1}];
Graphics[Inset[hcpii4plot, Center, Center, ImageScaled[1]], 
 Epilog -> {Text[Style["x", FontSize -> 20], 
    ImageScaled[{0.03, .33}]], 
   Text[Style["y", FontSize -> 20], ImageScaled[{.97, .33}]], 
   Text[Style["z", FontSize -> 20], ImageScaled[{.5, .99}]]}]
BarLegend[{"DarkRainbow", {MinValue[
    hcpii4angfunc[\[Theta], \[Phi]], {\[Theta], \[Phi]}], 
   MaxValue[hcpii4angfunc[\[Theta], \[Phi]], {\[Theta], \[Phi]}]}}, 
 LegendLayout -> "Row", LabelStyle -> Directive[Black, 14]]

Any help would be greatly appreciated!