Add information about GA4 custom event naming (#2999)

Author: markzegarelli

src/connections/destinations/catalog/actions-google-analytics-4/index.md

@@ -65,9 +65,9 @@ Segment recommends using the prebuilt mappings when possible, however the Segmen
 In addition to recommended events, you can also send custom events using the [Custom Event action](/docs/connections/destinations/catalog/actions-google-analytics-4/#custom-event). Custom events are events that you name. Custom events don't appear in most standard reports; you need to set up custom reports for meaningful analysis. To create custom events in the Google Analytics 4 web interface, see Google’s [Modify and create events through the user interface](https://support.google.com/analytics/answer/10085872){:target='_blank'}.
 
 > info "Event naming limitations"
-> Google Analytics 4 requires that all event names contain only alpha-numeric characters and underscores, and must start with an alphabetic character. Segment replaces spaces in Event Names with an underscore, so that these events are accepted by GA4. For example, Segment renames an event named `Home Profile` to `Home_Profile`. In some cases, GA4 may reject an event outright, due to unsupported characters. For example, an event named `Home | Profile` will be silently rejected due to the pipe character.
+> Google Analytics 4 requires that all event names contain only alpha-numeric characters and underscores, must start with an alphabetic character, and support a maximum of 40 characters. Segment replaces spaces in Event Names with an underscore, so that these events are accepted by GA4. For example, Segment renames an event named `Home Profile` to `Home_Profile`. In some cases, GA4 may reject an event outright, due to unsupported characters. For example, an event named `Home | Profile` will be silently rejected due to the pipe character.
 
-In all cases, event names in GA4 are case sensitive. The Custom Event action includes a **Lowercase Event Name** option, to ensure consistency of all events sent to Google. For more information, see Google's articles [Google Analytics 4 event name rules](https://support.google.com/analytics/answer/10085872?hl=en&ref_topic=9756175#event-name-rules){:target='_blank'} and [Event name limitations](https://developers.google.com/analytics/devguides/collection/protocol/ga4/sending-events?client_type=firebase){:target="_blank"}.
+In all cases, event names in GA4 are case sensitive and require values in all properties. The Custom Event action includes a **Lowercase Event Name** option, to ensure consistency of all events sent to Google. For more information, see Google's articles [Google Analytics 4 event name rules](https://support.google.com/analytics/answer/10085872?hl=en&ref_topic=9756175#event-name-rules){:target='_blank'} and [Event name limitations](https://developers.google.com/analytics/devguides/collection/protocol/ga4/sending-events?client_type=firebase){:target="_blank"}.
 
 #### Custom Dimensions and Metrics
 With Google Analytics 4, you must create custom dimensions and metrics within the Google Analytics 4 interface and link parameters to the corresponding dimension or metric. When you create the dimension or metric, you can either select a parameter from the list of already collected fields or enter the name of the parameter you plan to collect in the future. Custom dimensions can be either event-scoped or user-scoped, and custom metrics must be event-scoped.