widget-documentation-link-p

widget-documentation-link-p is a variable defined in `wid-edit.el'.
Its value is

intern-soft

Documentation:
Predicate used to test if a string is useful as a link.
The value should be a function. The function will be called with one
argument, a string, and should return non-nil if there should be a
link for that string.

You can customize this variable.