• Update action message like this in Zabbix 4.0

  {test:web.test.rspcode[test,test].last()}
  {{HOST.HOST}:web.test.rspcode[test,test].last()}
  {HOST.HOST}
  
  {test:vm.memory.size[].last()}
  {{HOST.HOST}:vm.memory.size[].last()}
  

• Upgrade to 6.0, you will see message changed to custom message like below, macro {HOST.HOST} disapeared from expression {?last(//web.test.rspcode[test,test])} and {?last(//vm.memory.size[])},lack of hostname.

  {?last(/test/web.test.rspcode[test,test])}
  {?last(//web.test.rspcode[test,test])}
  {HOST.HOST}
  
  {?last(/test/vm.memory.size[])}
  {?last(//vm.memory.size[])}
  

If it is designed behavior, I think we should mention it in the document.