This extension for Visual Studio Code (https://code.visualstudio.com) allows you to edit AGS scripts directly from there with syntax, taking advantage of editing features that may be lacking in the AGS editor.
It does not provide auto-complete of AGS globals (rooms, characters, etc). The extension is unaware of the AGS scripting API or what is in your game. It may autocomplete with existing items it can find in the project, but it will not be as robust as what the Editor provides.
Download, release notes, and install instructions here:
https://github.com/clickpulp/vscode-ags-script/releases/tag/v1.0.0-alpha.0
https://github.com/clickpulp/vscode-ags-script/releases/tag/v1.0.0-alpha.0
THIS IS AN ALPHA VERSION, HELP ME TEST AND REPORT BUGS

I'm looking for people to test it out and report any bugs or give feedback in this thread or the Github issues for the project: https://github.com/clickpulp/vscode-ags-script/issues