I was an APL monkey at IBM for 9-ish months…
APL is a notation that is useful for mathematical thinking.
Mathematical notation (thinking) does not apply everywhere.
We (the royal we) think that multitasking is hard because we’re trying to do it in mathematical notation.
In fact, everyone already knows how to do multitasking.
The best (so far) notation for multitasking is a musical score. It denotes realtime, multiple parallel processes. OTOH, musical notation has the same problem as mathematical notation has — it was invented for 2D pen-and-paper, not 3D thinking.
Our problem is that we conflate “notation” with “programming”. We try to force-fit all of programming into one notation.
 I took down all of IBM Toronto (Canada?) writing a simple APL program (on a 5100). Turns out that there was a bug in IBM APL. OTOH, I was paid overtime to light up all of the front-panel lights on a 360 without trying.
 Think “cooking recipes”, “music"