An aspect that’s missing from the overall discussion here is that of the commonplace book. Edwards’ Miscellanies is a classic example of the Western note taking and idea collecting tradition of commonplace books.
While the name for his system is unique, his note taking method was assuredly not. The bigger idea goes back to ancient Greece and Rome with Aristotle and Cicero and continues up to the modern day.
From roughly 900-1300 theologians and preachers also had a sub-genre of this category called florilegia. In the Christian religious tradition Philip Melanchthon has one of the more influential works on the system: De locis communibus ratio (1539).
You might appreciate this article on some of the tradition: https://blog.cph.org/study/systematic-theology-and-apologetics/why-are-so-many-great-lutheran-books-called-commonplaces-or-loci
You’ll find Edwards’ and your indexing system bears a striking resemblance to that of philosopher John Locke, (yes that Locke!): https://publicdomainreview.org/collection/john-lockes-method-for-common-place-books-1685