Zabbix Proxy Server Debug one host/item only

[TheDon]

When enabling debug mode on a Proxy Server, one gets a lot of data. We have thousands of hosts that we monitor.
The obvious problems include log size getting far too big and the amount of data that is being captured is not relevant to the host and item I'm trying to troubleshoot.
...

[wsanders]

I am trying to debug problems with some users getting multiple emails and pages for an event, and other not getting anything.

I have enabled "Debug Mode" in the User Groups of interest. What does this do? It does not seem to increase log verbosity in zabbix_server.log.
...