Sadly there’s no way to add spacers or fieldsets at this point - although it’s a great idea.
In terms of creating a fieldset type boundary, you could add a box element with a background color or just a border (with a transparent background) and position that to group related form elements.
This won’t give you proper spacing between the elements, but it will allow you to group them.
To achieve some extra spacing you can use the “field spacing” property on the right hand panel when the form is “selected” - but this will push spacing between all fields.
Hope that helps in some way.
Note: if you have a background color on the box, you’ll need to hit the “back” button in the toolbar to push it behind the form element.