How detailed were your outlines when writing ASLH?
It really depended, they got more detailed as I wrote on. I'm not sure if this quite answers your question, but here's my process! Generally, I'd break things into broad levels of detail:
The outline I wrote for the whole story focused on a few specific story beats, like the ch3 case, the mastermind reveal, and certain deaths. I had a clear vision for specific moments and a general idea of what arcs I wanted certain characters to go through, but the clearest scenes were all at the beginning of the story. As I wrote, I'd often think of more specific scenes or plot lines that I wanted to resolve, and I made sure to write them down somewhere (mostly in a planning Discord I had with some friends, I found the different channels really helpful for organizing information). I don't think I actually wrote a full outline for the story at any point, I think I just infodumped everything once in a server and then copy/pasted that to make my outline LOL
Once I actually got to the casing chapter in question, the bullet point outline that I wrote went into more depth about specific storylines I wanted to hit. Well, to be honest, I didn't do one of these for ch1-3, because I didn't have a writing process then, there were a lot fewer storylines to keep track of, and I didn't fully know how I wanted my characters to develop at that point. After ch4, having a bulleted outline became necessary. There's obviously the culmination of the killer and victim's storylines, but I also had to keep track of things like the overarching mastermind plot/storyline or specific character beats that I wanted to integrate. I didn't do this back then, but nowadays I'll also attach things like playlists or images to my outlines to get a general sense of what I want the case to "feel" like.
From the broad strokes of my casing chapter, I'd decide how I wanted to pace the chapter (like, how many daily life chapters felt appropriate), and I'd also have a general sense of the scenes I wanted - whether it was something as specific as "conversation between these two characters when they're doing this specific thing that touches on xyz topics" to "I think we're gonna need a scene with this guy's character arc I don't have any big plot things planned for them". A rule of thumb I like to follow is that each story chapter should have at most one high-tension moment that advances either the mastermind/worldbuilding plot, the killer/victim plot, or a central character dynamic in a major way. If I put more than one high-tension moment in a chapter, I ran the risk of cheapening either moment since there was no feeling of normalcy/status quo to contrast the reveal with. (Sometimes, like the first half of 5-1, there were plot-advancing scenes that didn't necessarily have an overemotional aspect to them. In this case, I'd consider the last scene of 5-1 to be the high-tension moment.) I'd divide these types of scenes among the daily life for pacing, or make a note of which things I wanted to be revealed in deadly life (occasionally with notes on how I wanted to do it). I wouldn't necessarily plan Every scene of every story chapter at this point, but I had a feel for what had to go where and what the general tone of each story chapter should be.
From there, once I got to the story chapter, I made a bullet point outline with the specific scenes I wanted in the chapter. In addition to the story beats that I came up with in the casing chapter outline, I also slotted in some filler events using underutilized characters to make the high-tension moment seem worthwhile, or to come down from that moment. I used these to either dump random characters to flesh out spontaneous dynamics which could be expanded upon as subplots later down the line (in ch1-3) or address subplots that hadn't been brought up in some time (in ch4-6). A beautiful byproduct of this process is that I got to delete the outline as I went along, which was extremely satisfying.
So basically, they got more detailed as I got to the points where each story element was relevant. I hope that's helpful!