Caustics are not included in the built-in list because they overlap with
indirectdiffuse lpe:C<RD>[DS]+[<L.>O] However, you can select caustics with the expression
lpe:CDS+[<L.>O] Below you can find an example of the caustics LPE output, Indirect Diffuse, and the difference between them. Note that the Caustics LPE output doesn't capture indirect lighting from object to object.
|Carousel Image Slider|
If a custom LPE is useful for your shots, you can add your custom LPE by creating a macro in
rendermn.ini file. The custom LPE will appear in the RenderMan for Maya (RfM) LPE list after relaunching Maya. For example: