In answer to your question, one way to generate a waveshaper from polynomial coefficients and save it as a lookup table is in the Wave Editor, using the Generate section with "polynomial" selected. Here's an example with the range set to [-1,1] and the coefficients set to varying strengths:
Once you get the shape you want, click Insert and save the result as a sample that you can use as the ShapingFunction parameter of the Waveshaper prototype.
For anyone curious to hear and see the impact of varying the coefficients of the polynomial waveshaper while it is shaping a sine wave input, you might enjoy experimenting with this example from the Kyma Sound Library:
/Kyma/Kyma Sound Library/Teaching demonstrations/Waveshaping lab
And if you get interested in waveshaping, try using the Sound Browser to search the Kyma Sound Library by Sound name 'wavesh' for a whole bunch more fun applications of waveshaping like wave folding.
Or search by Sound class name for "inputout" to find examples of the InputOutputCharacteristic which is a more general form of waveshaping (not limited to polynomial functions) and can be used for all kinds of fun distortions (of waveforms, amplitude envelope, or even rhythmic patterns and pitch distributions).