I needed this for a side project and i'm placing this script here. It gives a baseline to modify a node's custom property via PowerShell and SWIS without the need to install the SDK. The baseline can be modified/imported into any current POSH script.
The end goal was the change a Node Custom Property called 'SendAlert' to either true(Yes) or false(No). Then use this custom property in the alert engine to "toggle" when nodes are allowed to alert. There are a lot of variables at play so the "Time of Day" scenario didn't quite fit.
You'll need to pass the node ID, ${Node.ID}, into the script.
In the alert trigger condition, in the scope section, i added the custom property.
Here is another link that goes into more detail around setting up a Custom Property in an alert.
I also have an example of how to change a APPLICATION custom property via Rest API.
PowerShell script to modify an APPLICATION Custom Property via Rest API/JSON
