Info request: how to update submitted form data?

[GeetsM]

We are currently migrating from AEM Foundation Forms Components to AEM Core Forms Components. We have a URL query param which should be inserted in the submitted form data json. To achieve this I created a custom javascript function which I call from within the rule editor. In this function I then try to update the form data.

I have found a working solution after deep-diving into the source code:
var param = new URLSearchParams(window.location.search).get('....'); window.guideBridge.getFormModel().importData(Object.assign({}, window.guideBridge.getFormModel().getDataNode().$value, {afUnboundData: {data: {"param": param}}}) )

But this is far from straightforward. Is there a better way to achieve this? Normally there is, for example, the setData() function on guideBridge (I believe) but that doesn't work for core components. Is there a core components variant to easily add something to the json data?
Thanks!

[rismehta]

@GeetsM Apologies for the delay. Ideally, you should use the following API to set this as additional submit metadata. It shouldn’t be part of the form data, as all form data should come from form fields only. This approach ensures that features like form prefill will work seamlessly as well.

var param = new URLSearchParams(window.location.search).get('....'); 
const additionalSubmitMetadata = window.guideBridge?.getFormModel()?.additionalSubmitMetadata;
window.guideBridge?.getFormModel()?.
setAdditionalSubmitMetadata({...additionalSubmitMetadata, param: param});