[FEATURE] Use Optical Flow for Frame interpolation with Speed Effect and Rate Stretch
Re-timing footage, Optical Flow is essential for smooth output. Many people want to stretch the duration of their footage, or re-time stock footage which they downloaded.
Other VFX programs have had this for years (I won't mention them here out of respect), and there are even some freeware programs that do a pretty good job at Optical Flow, although their interfaces can be clunky and confusing.
I'm sure the programmers at HFP would do a great job.