Is there any native or plugin field that would allow multiple selections of data which can then be sorted? This would not be posts but rather a list of elements derived via a service.
Something like the relationship field UI would be close. Where I can dynamically set the list on the left; drag selections to the right and then sort the selections on the right. Obviously retaining the selections and their order.
The select field in ACF5 has a “Stylised UI” setting. This will not give the left/right drag feature, but it will retain the order of the selections made when getting the value of the field.
There isn’t anything for ACF that does exactly what you want, at least not that I know of.