Salam visionary
The witr prayer is mentioned specifically in the secondary sources, the ahadith corpus. It is note fard, but also not sunna. But stronger than a Sunnah. According Hadith not good, to leave that prayer. according ahaadeeth too, you can pray three five or seven or nine rakaas as long as they are odd. According a hadith which says that Allah, because He is Witr (one) He loves the witr.
In the Koran there is no such prayer. For me, that hadith seem to indicate on voluntary night prayer. (which will be treated in the secondary sources as a separate prayer.)
I hope that my answer could help you? Or you wanted to know something else?peace and Salam