org-speed-commands-user

org-speed-commands-user is a variable defined in `org.el'.
Its value is

nil

Documentation:
Alist of additional speed commands.
This list will be checked before `org-speed-commands-default'
when the variable `org-use-speed-commands' is non-nil
and when the cursor is at the beginning of a headline.
The car if each entry is a string with a single letter, which must
be assigned to `self-insert-command' in the global map.
The cdr is either a command to be called interactively, a function
to be called, or a form to be evaluated.
An entry that is just a list with a single string will be interpreted
as a descriptive headline that will be added when listing the speed
commands in the Help buffer using the `?' speed command.

You can customize this variable.