I really like to use HPGLM node. But I am not very familiar with proc glimmix to be honest.
Google the paper below. The author makes really good comparison about all the available linear models in SAS.
From GLM to GLIMMIX-Which Model to Choose?
Patricia B. Cerrito, University of Louisville, Louisville, KY
If for some reason you really like to use proc glimmix, you can use a SAS Code Node, or even code your own "glimmix" node.
I hope this helps,
Miguel