To distinguish between a GraphQL query with one set of curly braces {...} and a handlebars expression with two sets of curly braces {{...}} , use double quotes ( " ") around the handlebars expression and the braces. This is especially required if the handlebars expression will populate a string. Proper formatting in your handlebars expression will help distinguish as well. For example, rather than:
{"target":{"UserId":{{record.customerId}}}}
use
{ "Target": { "UserId":{{record.customerId}} } }