If you have your visual editor set to Vim (e.g. set VISUAL=vim in your .bashrc, or before opening IEx), then pressing Ctrl+o will allow you to edit the current command in Vim.

It depends on what you mean with vi bindings, but having different modes such as vi is not possible.

You can however configure other bindings if you wish, that is described here: edlin — OTP 29.0.3 (stdlib 8.0.2). Maybe you can do something with that which makes it simpler for you?

For me this is one of the many reasons why I’ve mostly moved towards using LiveBook for most of the stuff I’d use IEx for. It’s obviously not a complete replacement, but with some adjustments to my workflow, it’s so much better in most ways /and/ it has pretty solid support for vim keybindings.

Generally I now just connect a livebook to my running project, and when possible, I do snippets of coding inside the livebook. In many cases just being able to see the output as a table is a godsent.