Activate the eye dropper tool and You can select the color you want and tap on the small plus icon on the bottom of the left toolbar to quickly add colors to the swatch. That’s 2 clicks just like in procreate and super easy/ fast, I create a big palette from a photo within a minute. Rearranging the colors is also possible by dragging them where you need them. And making palettes from photos automatically also works in ASP with more control than in procreate, I don’t know why you say it’s ridiculously slow, it works very well