Do you mean set encoding or convert? because where is an option to convert encoding? Also I use Linux, so what equivalent could do in linux as in gedit I don't see a way to convert encoding from one to another.

With notepad++ you can encode and convert. see updated image. But it is Windows application. I'm sorry... There must be something equivalent for linux too...

I found a Linux way. See my updated answer. I hope it works, I cannot try it...

I was able to convert encoding simply creating new csv file with utf-8 encoding, then copying everything there. I previously tried something similar with libreoffice, but that didn't work.