Usually, I do this while writing the draft, adding each new scene as needed, however, this time, I've been using the set-up to outline instead. I create the text file for the scenes I need and then write a point-form break down of what should happen in it in the synopsis box provided on the top right corner.
This is allowing me to break down the book scene by scene where I can still see the general layout of the whole book in the pane on the left, while also being able to click on any given scene to get a more detailed rundown.
This makes it easy to jump around in the outline—adding and rearranging things as needed—and also allows me to write notes and reminders to myself directly in the file I will later be writing in. For example, if I want a character to have a particular reaction to a certain event, I can add it as a 'note to self' in the synopsis or notes section of the scene file.
The best part about this method is it means that when I actually sit down to write the scene, I'll have all of the information I need right there in front of me. One of the problems with my previous methods of outlining is that I have lots of little ideas about how scenes should play out while I'm working on the outline (too many to make each one its own bullet point without the outline becoming overwhelming) but its very unlikely I'll remember all of those details by the time I get to drafting. Using this method, I can keep track of all my thoughts and ideas for a scene, and will have access to them when I actually need them!
I've included an example of my current method below. You can see here how I've got the scenes prepared in the binder on the left, even though I haven't done any actual writing in them, while the synopsis on the right contains my more detailed breakdown of the scene.
(WARNING: Mild spoilers for previous books can be found in the written details of these next few pictures, so read at your own discretion!)