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To identify code usage we have a references report:
https://portalgreatmigrations.greatmigrationsatlassian.comnet/wiki/display/GMG/Semantic+Model+Reports
To remove the definition and, optionally the use, of a symbol we have the Refactor/Remove command:
https://portalgreatmigrations.greatmigrationsatlassian.comnet/wiki/display/GMG/gmplRemoveStatement
These two capabilities could be synthesized using our gmSL scripting language to automate the process:
https://portalgreatmigrations.greatmigrationsatlassian.comnet/wiki/display/GMG/gmSLIntroduction
See also Support Statement: Unused Symbol Analysis and Reporting