I'm trying to solve the following issue:
Notifications for triggers (created by SNMP LLD) for a network device (load balancer) must be routed to different user groups / teams. The only possibility I saw to achieve that without touching the action condition every time the LB config changes was to "abuse" the description field exposed via SNMP as event tag value (it contains the team to notify). So every trigger created by SNMP LLD has a tag "Team" containing the description provided by the LB via SNMP.

Now my plan was to create one or more actions per team, using the "Tag value" action condition. "Tag value" "Team" = "team01" works as intended. But we need a fallback action in case we missed configuration for a team. So I tried to extend the action notifying my team with multiple action conditions like "Tag value" "Team" <> "team01", "Tag value" "Team" <> "team02" and so on to blacklist all known teams and only match unknown/new teams.
After some debugging I found out that "Tag value" tag name <> tag value ONLY matches if the event has a tag with the corresponding name attached. That makes it incredibly hard to configure something like a "tag value blacklist" and still match events without any tags at all.

I tried to work around the problem by using an expression like (Tag <> Team or (Tag value Team <> team01 and Tag value Team <> team02 and …)), but that doesn't work because of ZBX-11310 (and it's not very readable at all).

If you think this works as intended I'd suggest migrating this bug report to a feature request.