With JavaScript

There are many ways to send data via JavasScript. This would be one of the easiest solutions:

<button onclick="submit()">Submit data</button>

<script>
  function submit() {
    let data = { name: 'Some name', someRandomData: 'some value' };
    fetch("https://plus.dropzone.dev/_p/{YOUR_PROJECT_ID}", {
      method: "POST",
      body: JSON.stringify(data),
      headers: { "Content-Type": "application/json" },
    });
  }
</script>

This encodes the data as JSON and sends it to Dropzone Plus. Please note that the Content-Type needs to be set appropriately for it to be recognized.