Должна быть вложенность и ","
{
"betterAlign.surroundSpace": {
"colon": [0, 1],
"assignment": [1, 1],
"arrow": [1, 1],
"comment": 2
}, //Должна быть запятая
"path-autocomplete.pathMappings": {
"@img": "${folder}/src/img", // alias for /test
"@scss": "${folder}/src/scss", // the absolute root folder is now /src,
"@js": "${folder}/src/js" // the relative root folder is now /src
}, // Сразу поставь на будущее ","
}