the dropdown list on sia.php is indeed incomplete, we should improve that. If you are using the DL notebook server, you can list all available SIA services with
from dl import queryClient as qc
And if you have the 'datalab' CLI installed locally (please make sure to update to the latest v2.20.0), then just do:
datalab services svc_type=sia
Both spit out a list that has short descriptions of the SIA services.
And of course, using the NB or CLI APIs allows you to script your image searches. There's an example NB in the collection (plus several other NBs have smaller examples): https://github.com/noaodatalab/notebooks-latest/tree/master/04_HowTos/SiaService/
Hope this is helpful,