There are a few dispatch specific arguments you can pass like bucket , max_count , earliest_time etc. You can get the full list at savedsearches.conf.
The parameters that you are trying to use are substituted slightly differently. Here is an example ...
Sample saved search query with host as one of the parameters that I want to substitute at runtime: index=fooindex sourcetype=foosourcetype host=$args.host$
Sample JS code to dispatch with argument substitution: mySavedSearch.dispatch({"args.host": "foohost"}, function(err, job) {
You can bind multiple parameters in the call above depending on your need. Remember to specify args along with your parameter name as mentioned above.
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