Great stuff! Nice novel indicator in 1D and 9A is masterfully hidden. I like what you’re doing in 8A, but I can’t find a source that has magpie as a verb or filch as a noun, so I’m not sure quite how that one works.
Oh yeah, I guess I can’t really find any references to it either outside of Wiktionary, but I’ve heard “magpie” used as a verb for stealing/hoarding, especially with like ideas, but yeah maybe that’s not a common usage.