引自 https://stackoverflow.com/questions/29968499/vertical-rulers-in-visual-studio-code
打開設置
File > Preferences > Settings
搜索 rulers
點擊 Edit in settings.json
添加一行
"editor.rulers": [80,120]
參考線顏色可以自定義
"workbench.colorCustomizations": {
"editorRuler.foreground": "#ff4081"
}