bs-sort-functions

bs-sort-functions is a variable defined in `bs.el'.
Its value is

(("by name" bs--sort-by-name "Buffer" region)
 ("by size" bs--sort-by-size "Size" region)
 ("by mode" bs--sort-by-mode "Mode" region)
 ("by filename" bs--sort-by-filename "File" region)
 ("by nothing" nil nil nil))

• This variable may be risky if used as a file-local variable.

Documentation:
List of all possible sorting aspects for Buffer Selection Menu.
You can add a new entry with a call to `bs-define-sort-function'.
Each element is a list of four elements (NAME FUNCTION REGEXP-FOR-SORTING FACE).
NAME specifies the sort order defined by function FUNCTION.
FUNCTION nil means don't sort the buffer list. Otherwise the function
must have two parameters - the buffers to compare.
REGEXP-FOR-SORTING is a regular expression which describes the
column title to highlight.
FACE is a face used to fontify the sorted column title. A value of nil means
don't highlight.

You can customize this variable.