I think the developers use different IDEs. there are people using simple text editors, there's probably at least one person using visual studio code, visual C++, intellij, vim, emacs. I bet someone coded a mod in notepad++ already, too
@Deleted User there is an undo function, you can't take back step by step but if you activate it by typing cl_editorundo 1 in f1 you'll get this Undolist button in editor, so you can load older versions of your mapping session
Are there server issues/maintenance or something right now? Most of the listings in the browser show 999 ping and aren't connectable or showing the server name