Can Elixir script or iex use external modules without creating a new project?

The Code module has functions to implement all the things you need. However, it only works with existing files on the machine and you'll need to do pretty much everything "manually".

Code.append_path

Code.ensure_loaded

should accomplish most of what you want.

Another approach is to use iex -S mix in an existing project with the dependencies and then load the .exs file.