The native tabs support currently only works when the OS-level system setting "Prefer tabs when opening documents" is set. I think it would make more sense to always open native tabs when the VS Code option window.nativeTabs is set to true.

The patch would be similar to the one I suggested in: microsoft/vscode#250042. Only we would look for window.nativeTabs instead of a new setting, which I opted for in this issue for backwards compatibility reasons.