下記のようにキーバインドを追加すればOK。
(※Windows/JISキーボード)
keybindings.json
{
"key": "shift+7",
"command": "editor.action.insertSnippet",
"when": "editorTextFocus && editorHasSelection",
"args": {
"snippet": "'$TM_SELECTED_TEXT$0'"
}
},
{
"key": "shift+2",
"command": "editor.action.insertSnippet",
"when": "editorTextFocus && editorHasSelection",
"args": {
"snippet": "\"$TM_SELECTED_TEXT$0\""
}
}