The new alert rule experience is a little different than the old experience.
Please note these changes below:
1) Previously, search results were included in the payloads of the triggered alert and its associated notifications. This was a limited and error prone solution. To get detailed context information about the alert so that you can decide on the appropriate action :
o The recommended best practice it to use Dimensions (https://learn.microsoft.com/en-us/azure/azure-monitor/alerts/alerts-unified-log#split-by-alert-dimensions). Dimensions provide the column value that fired the alert, giving you context for why the alert fired and how to fix the issue.
o When you need to investigate in the logs, use the link in the alert to the search results in Logs.
o If you need the raw search results or for any other advanced customizations, use Logic Apps.
2) The new alert rule wizard does not support customization of the JSON payload.
o Use custom properties in the new API (https://learn.microsoft.com/en-us/rest/api/monitor/scheduledqueryrule-2021-08-01/scheduled-query-rules/create-or-update#actions) to add static parameters and associated values to the webhook actions triggered by the alert.
o For more advanced customizations, use Logic Apps.
3) The new alert rule wizard does not support customization of the email subject.
o Customers often use the custom email subject to indicate the resource on which the alert fired, instead of using the Log Analytics workspace. Use the new API (https://learn.microsoft.com/en-us/azure/azure-monitor/alerts/alerts-unified-log#split-by-alert-dimensions) to trigger an alert of the desired resource using the resource id column.
o For more advanced customizations, use Logic Apps.
Reference:
https://learn.microsoft.com/en-us/azure/azure-monitor/alerts/alerts-log