To fixed size in file, go to Command + Shift + P Go to: "Preferences: Open User Settings (JSON)"
Paste the code below;
"editor.fontSize": 16
To control using Command + +, Go to: Command + Shift + P > Preferences: Open Keyboard Shortcuts (JSON)
Paste the code below;
{
"key": "cmd+=",
"command": "editor.action.fontZoomIn"
},
{
"key": "cmd+-",
"command": "editor.action.fontZoomOut"
},
{
"key": "cmd+0",
"command": "editor.action.fontZoomReset"
},
{
"key": "cmd+=",
"command": "-workbench.action.zoomIn"
},
{
"key": "cmd+-",
"command": "-workbench.action.zoomOut"
}





