resolved - just like you said - added the json one line into the search bar of the graph:
{"query":{"query_string":{"query":"ses_slowq_rtime:>100.0","analyze_wildcard":true}}}
Also had to flatten the script so there are no new lines and carriage returns.
Thank you - also thanks to my coworker Brad for pointing out that this goes into the top search bar and not into the JSON section inside the Advanced part of the graph build area.