where-is-preferred-modifier

where-is-preferred-modifier is a variable defined in `C source code'.
Its value is

nil

Documentation:
Preferred modifier key to use for `where-is'.
When a single binding is requested, `where-is' will return one that
uses this modifier key if possible. If nil, or if no such binding
exists, bindings using keys without modifiers (or only with meta) will
be preferred.