The plotting of all the activation functions is done within a single function, remarkably titled PlotAllFunctions:

private void PlotAllFunctions()
{
// First, clear out any old GraphPane's from the MasterPane
collection MasterPane master = zed.MasterPane;
master.PaneList.Clear();
// Display the MasterPane Title, and set the 
  outer margin to 10 points
master.Title.IsVisible = true;
master.Margin.All = 10;
// Plot multiple functions arranged on a master pane.
PlotOnMasterPane(Functions.LogisticApproximantSteep,
  "Logistic Steep (Approximant)");
PlotOnMasterPane(Functions.LogisticFunctionSteep,
  "Logistic Steep (Function)");
PlotOnMasterPane(Functions.SoftSign, "Soft Sign");
PlotOnMasterPane(Functions.PolynomialApproximant,
  "Polynomial Approximant");
PlotOnMasterPane(Functions.QuadraticSigmoid,
  "Quadratic Sigmoid");
PlotOnMasterPane(Functions.ReLU, "ReLU");
PlotOnMasterPane(Functions.LeakyReLU, "Leaky ReLU");
PlotOnMasterPane(Functions.LeakyReLUShifted,
  "Leaky ReLU (Shifted)");
PlotOnMasterPane(Functions.SReLU, "S-Shaped ReLU");
PlotOnMasterPane(Functions.SReLUShifted,
  "S-Shaped ReLU (Shifted)");
PlotOnMasterPane(Functions.ArcTan, "ArcTan");
PlotOnMasterPane(Functions.TanH, "TanH");
PlotOnMasterPane(Functions.ArcSinH, "ArcSinH");
PlotOnMasterPane(Functions.ScaledELU, 
  "Scaled Exponential Linear Unit");
// Refigure the axis ranges for the GraphPanes.
  zed.AxisChange();
// Layout the GraphPanes using a default Pane Layout.
using (Graphics g = this.CreateGraphics()) {
  master.SetLayout(g, PaneLayout.SquareColPreferred);
}