根据文档：
A list ends whenever every item has ended, which means before any line less or equally indented than items at top level. It also ends before two blank lines. In that case, all items are closed. Here is an example:
org-mode 中使用两个空行来分隔不同的 plain list，间隔一个空行的 list 会被当作是同一个。比如下面的 a 和 b 对 org-mode 来说就是一个 list。
- a
- b
想知道如何修改为使用一个空行来分隔。
在 org.el 源码中有找到这个代码，但是把 2 修改成 1 之后重编译无效。
(cond
;; Two blank lines end a footnote definition or a plain
;; list. When we indent an empty line after them, the
;; containing list or footnote definition is over, so it
;; qualifies as a previous sibling. Therefore, we indent
;; like its first line.
((and (memq type '(footnote-definition plain-list))
(> (count-lines (point) pos) 2))
版本信息：
- org-mode 9.6
- Emacs 27.2