[idvusers] grib1 files/ dead documentation link

I have been trying to display a grib1 file that shows the probability of qpf >= .1" . IDV won't display this because it seems to think I am trying to display zonal gravity wave stress so there must be something wrong with my parameter table? I've looked in the IDV help guide (7.4.3) to try to "add new GRIB tables", but there is a dead link to the documentation on parameter tables.

Is adding new GRIB tables what I should be looking to do? If so, is there any information on creating GRIB tables?