src/vs/workbench/browser/parts/notifications/notificationsCenter.ts/NotificationsCenter/clearAll
class NotificationsCenter:	clearAll(): void {

		// Hide notifications center first
		this.hide();

		// Close all
		for (const notification of [...this.model.notifications] /* copy array since we modify it from closing */) {
			if (!notification.hasProgress) {
				notification.close();
			}
		}
	}