org-alphabetical-lists

org-alphabetical-lists is a variable defined in `org-list.el'.
Its value is

nil

• This variable is an alias for `org-list-allow-alphabetical'.
• This variable is obsolete since 24.4;
  use `org-list-allow-alphabetical' instead.

Documentation:
Non-nil means single character alphabetical bullets are allowed.

Both uppercase and lowercase are handled. Lists with more than
26 items will fallback to standard numbering. Alphabetical
counters like "[@c]" will be recognized.

This variable needs to be set before org.el is loaded. If you
need to make a change while Emacs is running, use the customize
interface or run the following code after updating it:

(when (featurep 'org-element) (load "org-element" t t))

You can customize this variable.