The gist is to just filter the lookup the countries not listed in the multiselect field.

I've been using a client script and this time I would like to set this criteria for the lookup:

op.setCriteria("((Specialty_Requirement:equals:" + spec + ")and(Countries_Excluded:not_equal:" + coo + "))", { filterOnSearch: true });

I'm getting the error

Operator not supported - not_equal

Is there a documentation on all possible operators supported and as well as the config options.

This documentation does not say a lot about this