You can modify master.xml at any time, but you must regenerate the application and redeploy the project after making any changes to the file. Use caution when updating this file after moving into production, since changing certain properties, such as the blocking query, can cause unexpected matching and weighting results. Most of the configuration options in this file cannot be modified using the Configuration Editor. The exceptions are the match and duplicate thresholds. The possible modifications to this file are restricted by the schema definition, so be sure to validate the file after making any changes.