Inline Entity Form Order by field value
I did it using hook_form_alter().

If you have a field with an inline entity form:

$form['field_newsletter_content'][LANGUAGE_NONE]['entities'];


Then you can change the '#weight' property on the individual entities.

So, to change the weight of element 0 to 1, do this.

$form['field_newsletter_content'][LANGUAGE_NONE]['entities'][0]['#weight'] = 1;


And if you change the weight of element 1 to 0, then they will have traded places in the inline entity form.