在path变量后添加，对变量长度无限制，需要重启后生效
reg add "HKLMSYSTEMCurrentControlSetControlSession ManagerEnvironment"
/v Path /t REG_SZ /d "%path%;c:
ewpath;whatever" /f
reg save "HKLMSYSTEMCurrentControlSetControlSession ManagerEnvironment" D:\path.hiv /y
reg export "HKLMSYSTEMCurrentControlSetControlSession ManagerEnvironment" d:MyReg.REG
reg import c:myreg.reg
SetX _car_park North /m
SetX aaa "%PATH%;foobar;" /m