I assume you know basics for Business events.
Actually, alert type of business events created a huge expansion for D365FSCM integration. Here is a Microsoft docs link for a general overview.
Business events overview – Finance & Operations | Dynamics 365 | Microsoft Docs
We can now trigger a logic app or publish the event to Event grid
Business events and Azure Event Grid – Finance & Operations | Dynamics 365 | Microsoft Docs
or publish data as message Azure Service bus
Business events and Azure Service Bus – Finance & Operations | Dynamics 365 | Microsoft Docs
so on. It is up to you now.
Unfortunately, organization-wide alerts don’t work with this structure.
To generate business event through Alerts you need to select “Send Externally” option and it enables after disabling “organisation-wide” option.
To enable Send Externally option you need to disable “Organisation-wide” option.
So you need to set up your alerts per legal entity.
Another tricky part is the filter.
If you want to apply an alert rule in certain conditions then you look for a place to put in.
There is a hidden setting for this. Alert rules work with the form’s filter which you set it up. So If you want to trigger an alert on PO’s which is approved and ordered by a certain person, then you need to set a filter on the PO screen, then create an alert rule. It will pick up filters automatically.
This brings another problem. You can not set an alert rule for all line type records inside of a header/line form.
For example, you can not set up a general purchase order line alert inside of a purchtable form. Because it will be filtered by purchid automatically.
This is same for expense lines.
There is a solution for purchase order lines. We have an inquiry screen for open order lines. you can set it up from that screen but you have to develop line based inquiry screen for expenses.
Hope this helps in your cases.