I started GMEdit over the terminal with electron (./electron)
This is an Electron bug, see here
https://github.com/GameMakerDiscord/GMEdit/issues/64
(and probably test/file a bug since the last person didn't seem to care at all)
Well, I don't know either - this isn't even in my code.
You could try using the mini-plugin I made for copying paths into clipboard as a workaround,
https://bitbucket.org/yal_cc/copy-path/src/master/
but I would highly suggest to test with Electron Fiddle and file a bug with them so that it's fixed at some point.
Here's a snippet to put in Render Process in Electron Fiddle to check:
const electron = require('electron')
let path = electron.remote.app.getPath("userData");
console.log(path);
electron.shell.openExternal(path);