Yes, you are correct.
In the changelog found on this page.
It’s written in version 2.6.0
– Added unlimited number of Parallax slides and reordering option
I checked the current version 2.6.4
Drag and Drop only works for Bootstrap slides and There is no Drag and Drop for Parallax Slider slides.
I will report this issue to our developers. Please wait for update in new Theme version.