Autodesk releases a new version every March. The --env.acad syntax has been stable since AutoCAD 2010, but the release name changes.
When AutoCAD resolves this, it dynamically builds the path list based on the release name the user launched. autodesk autocad --env.acad release name-
--env.acad %ACAD_CURRENT_RELEASE%\Plugins\CustomAPI.arx --env.acad %ACAD_CURRENT_RELEASE%\Plugins\DatabaseExtension.dbx --env.acad %ACAD_CURRENT_RELEASE%\Support\Startup.lsp Autodesk releases a new version every March
Inside your Acad.rx file, you write: --env.acad release name-\myplugin.arx you write: --env.acad release name-\myplugin.arx