todo-files-function

todo-files-function is a variable defined in `todo-mode.el'.
Its value is

todo-files

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

Documentation:
Function returning the value of the variable `todo-files'.
This function should take an optional argument that, if non-nil,
makes it return the value of the variable `todo-archives'.

You can customize this variable.