The Prophet ﷺ offered the Maghrib and ʿIsha' prayers together at Jam' (i.e. Al-Muzdalifa) with a separate Iqama for each of them and did not offer any optional prayer in between them or after each of them.
جَمَعَ النَّبِيُّ ﷺ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ بِجَمْعٍ كُلُّ وَاحِدَةٍ مِنْهُمَا بِإِقَامَةٍ وَلَمْ يُسَبِّحْ بَيْنَهُمَا وَلاَ عَلَى إِثْرِ كُلِّ وَاحِدَةٍ مِنْهُمَا