In Reports → Triggers top 100 you can see the triggers that have changed their state most often within the period of evaluation, sorted by the number of status changes.
Both host and trigger column entries are links that offer some useful options:
You may use the filter to display triggers by host group, host, trigger severity, predefined time period or a custom time period.
Specifying a parent host group implicitly selects all nested host groups since Zabbix 3.2.2. In Zabbix 3.2.0, 3.2.1, nested host groups are selected if the parent group is specified by a
parent group/* syntax.