Personally, I think it’s importnt to differentiate between Ahrens’ ideas and those of Luhmann; the book isn’t always clear about the distinction. I’d take the Luhmann position and ask “Do you want to?”. You either have something you want to say, or express in a more personally meaningful way or you don’t. If you don’t then making yourself do it is simply make work.
If working with long notes and headings suits you, then why do you want to break a bit off? An atomic note is an atomic note, whether it is in a file on its own or under a heading in a bigger file.
So, if I have more thoughts triggered by that note, I’d write them and then link back to the starting point note. That would be closer to the folgezettel system.