You can pull that off relatively easily using Value Triggers which we already have in place. It allows you to script JavaScript when it is moving to the next item. So in your case you would attach a Value Trigger to the last item in the Run-up check.
You can create functions in the Functions panel if you select the top-level node in your outline. Here is an example function showing how to do a fetch. You could also do a POST if you want to send a payload.
This function is getting weather values from an api, but of course you can simulate a webhook.
async function fetchKIndices() {
const response = await fetch('https://services.swpc.noaa.gov/products/noaa-planetary-k-index.json');
if (!response.ok) {
const message = `An error has occured: ${response.status}`;
mcAlert.alert(message);
}
const kIndices = await response.json();
mcAlert.alert(JSON.stringify(kIndices));
}
You can then call the function in the Value Trigger panel on any item…
fetchKIndices();
More info on Value Triggers…
Let me know how it goes with what you are trying to do.