Related to: https://support.zabbix.com/browse/ZBX-4302

Currently it is not possible to add a trigger with an expression which has more than 255 characters.

In my case, my trigger expression is fine within the template (trigger is defined in a Template), it is less 255 characters long.
But assigning that Template to a Host fails, as the Hostname is longer than the Template Name. Therefore the Trigger expression will be longer than 255 characters.

The Frontend error looks like:
ERROR: Cannot update host
Value "'{hostname.subdomain.example.com:Item_Name.2.3.12.1.2.["

{#SNMPINDEX}"].strlen(0)}<0|{hostname.subdomain.example.com:Item_Name.2.3.12.1.4.["{#SNMPINDEX}

"].change(0)}=1&({hostname.subdomain.example.com:Item_Name.2.3.12.1.4.["

{#SNMPINDEX}"].str("Active")}=1|{hostname.subdomain.example.com:Item_Name.2.3.12.1.4.["{#SNMPINDEX}

"].str("Disconnected")}=1)'" is too long for field "expression" - 275 characters. Allowed length is 255 characters.