While many things in the frontend can be configured using the frontend itself, some customizations are currently only possible by editing a definitions file.
This file is
defines.inc.php located in /include of the Zabbix HTML document directory.
Parameters in this file that could be of interest to users:
Minimum graph period, in seconds. One minute by default.
Default location of Y axis in simple graphs and default value for drop down box when adding items to custom graphs. Possible values: 0 - left, 1 - right.
String used as the name of the Zabbix frontend session cookie.
TTL timeout in seconds used to invalidate data cache of Vault response. Set 0 to disable Vault response caching.
Number of subfilter values per group (For example, in the latest data subfilter).