The 2021 book The Nature of Middle-earth, edited by Carl F. Hostetter, contains a large number of Tolkien manuscripts not previously published. Part 1 of the book in particular represents a single collection of texts, titled by Tolkien as "Time and Aging": an in-depth study on how to make the timeline and aging of the early Elves line up with what Tolkien wanted to happen.

The "Time and Aging" manuscripts appear to be mostly presented in the order Tolkien arranged them, but this is not their sequence of composition. Worse, in several cases the drafts within a chapter are presented out of sequence - in Chapter XVII, text 2 predates both 1 and 3. Unfortunately, most of the texts are undated. If you want to identify which idea was Tolkien's latest, or trace how a specific element of the texts evolved, you need to follow the clues in the text themselves. This is a daunting job - but luckily for you, the Barrow-Downs forum has done it for you.

All references are to the chapter or sub-chapter within Part 1 of The Nature of Middle-earth, except where given in [square brackets].