<form id="formId"> 
    <p><label for="q-name" id="q-name-label"></label><input type="text" name="name" id="q-name"></p>
    <p><label for="q-age" id="q-age-label"></label><input type="text" name="age" id="q-age"></p>
    <p><input type="submit" value="Apply"></p>
</form>
<!-- ... -->

function insertLine(subDocument, text, question, inputId, position) {
    var textInterval = subDocument.insertText(position, DevExpress.RichEdit.Characters.ParagraphBreak + text);
    var name = ' DOCVARIABLE FILLIN ';
    var field = subDocument.fields.create(textInterval.end, name + '"' + inputId + '" "' + question + '" ');
    field.isShowCode = false;
    return new DevExpress.RichEdit.Interval(textInterval.start, field.interval.end - textInterval.start);
}

var subDocument = richEdit.selection.activeSubDocument;
richEdit.beginUpdate();
richEdit.history.beginTransaction();
var lineInterval = insertLine(subDocument, 'Name: ', 'Enter your name ', 'q-name', richEdit.selection.active);
lineInterval = insertLine(subDocument, 'Age: ', 'Enter your age ', 'q-age', lineInterval.end);
richEdit.endUpdate();
richEdit.history.endTransaction();

richEdit.events.calculateDocumentVariableAsync.addHandler(function(s, e) {
    var map = {};
    for(var data of e.data)
        if(data.variableName == 'FILLIN') {
            var inputId = data.args[0];
            var question = data.args[1];
            $('#' + inputId + '-label').text(question);
            map[inputId] = data.callback;
        }
        else
            // you should calls all callbacks here
           data.callback('');
    $("#formId").on('submit', function (event) {
        event.preventDefault();
        for (var inputId in map) {
            if (Object.prototype.hasOwnProperty.call(map, inputId)) {
                var inputResult = $("#" + inputId).val();
                map[inputId](inputResult);
            }
        }
    });
});

richEdit.loadingPanel.show();
richEdit.document.fields.updateAllFields(function() {
    richEdit.loadingPanel.hide();
    console.log('update finished');
}, new DevExpress.RichEdit.UpdateFieldsOptions(true));