I came across your APL study session videos while exploring the other material. I used APL professionally for about a decade back in the early 80's. I am always pleasantly surprised when I see interesting work being done in APL. Interestingly enough I always thought APL would eventually evolve into a central language for AI. There were attempts at designing hardware-based APL machines way back when. Of course, much as the language, they were ahead of the technology of the times.
I don't do much with APL these days. I do keep it around for quick calculations and exploration, far more so than doing any projects. In many ways, a thinking tool of sorts.