While the configuration UI of Home Assistant is still in development, you can use this small webapp to modify your configuration. It's essentially an embedded Ace editor, which has syntax hightlighting and automatic linting for yaml files (and a ton of other features you can turn on and off). There is also an integrated file browser to select whatever file you want to edit. When you are done with editing the file, click the save-button (or hit CTRL+s/CMD+s) and it will replace the original file. JT Martinez has done a wonderful job by implementing Material Design. If there is anything you want to have differently, feel free to fork and enhance. And if something is not working, create an issue here and I will have a look at it. WARNING: This tool allows you to browse your filesystem and modify files. So be careful which files you edit, or you might break critical parts of your system.