Unfortunately, it seems that currently formValues only takes one set of inputs. However this has been a requested feature and we are working on improving the API to support more use cases.
The Wix Events v2 API will support this use case soon, but is still currently under Developer Preview so it isn’t recommended for use in production. Keep an eye out for its stable release. If you have any other suggested features or want to stay updated with upcoming changes, take a look at the Wix Roadmap.
It will send the form twice, but in one of them you’ll see your overwritten data. Important: don’t try adding fields here, use previously defined fields in your Wix Form