Form configuration

Is it possible to load the form configuration from an external file as in version 5.1 ?

No, such featrure is not supported.
But you mayu load your config to the client-side using the ajax.request, and parse the resul;t to the form constructor.

dhx.ajax.get(url).then(function (data) {
   var form = new dhx.Form("form_container", {data});