How do I search by a field other than the label?

By default, search matches against labelField. To search a different field, set searchField.

<Dropdown
  search
  data={users}
  labelField="name"
  valueField="id"
  searchField="email"
  placeholder="Pick a user"
  searchPlaceholder="Search by email…"
  onChange={(user) => setUser(user)}
/>

Now typing in the search box filters the list by user.email while the visible label stays as user.name.

Multiple fields?

If you need to match across several fields, or apply normalization (accents, locale, trimming), use the custom matcher — see Custom search matcher.