Visual Studio Code (VSCode) is an open source edition released by Microsoft, with a special focus for development. It is an Electron application, therefore it can run on many operating systems, including Linux and MacOS (hint: if you want to give it a try, be sure you disable telemetry reports in case you want strict privacy).
If you are using it for editing kamailio.cfg, you may consider installing the extension for syntax highlighting. It can be installed from VSCode marketplace:
Editing kamailio.cfg should look like next image (on a dark blue theme).
If you are using a different editor, note that there are kamailio.cfg syntax highlighting extensions for VIM, MCEdit and Atom. Contributions for other editors or enhancements to existing ones are very welcome!