.conf

my_app.complex_list = {buzz, person}, {fido, dog}

schema.exs

[mappings: [
  "my_app.complex_list": [
    to: "my_app.complex_list",
    datatype: [list: :opaque],
    default: []
  ]
  ],
 translations: [
   "my_app.complex_list": fn
		_, values, conf_acc ->
		  Enum.map(values, fn({name, type}) ->
		    [name: name,
		     type: type]
		  end)
		end
 ]]

sys.config

[{my_app,
    complex_list, [
      [{name, buzz},
       {type, person}],
      [{name, fido},
       {type, dog}]
       ]}
]