Hi there! I haven’t really got into jazz hap even though it is something I am interested in so I might not be able to help much. I thought I would share some jazz harp resources that I have came across that you might find helpful.
1) Deborah Henson-Conant is a very well known jazz harpist. She has loads of contents in her Hip Harp Academy, many of which are based on jazz and improvisations. https://www.hipharp.com/academy/
2) The Berklee Harp Book was written by harpist Felice Pomeranz who is also known for jazz harping. https://berkleepress.com/strings/berklee-harp/ This book is specific written for the harp and the exercises and examples are designed to use with the harp.
I am not heavily invested in learning jazz harp theory at the moment because I’ve got quite enough harp stuff to occupy myself. I’m happy to connect though if you are okay with someone who is needs to take some time with the learning!