'sort-buffers-menu-by-mode-then-alphabetically
"*If non-nil, a function to sort the list of buffers in the buffers menu.
It will be passed two arguments (two buffers to compare) and should return
-T if the first is \"less\" than the second. One possible value is
+t if the first is \"less\" than the second. One possible value is
`sort-buffers-menu-alphabetically'; another is
`sort-buffers-menu-by-mode-then-alphabetically'."
:type '(choice (const :tag "None" nil)