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. (Using translation from Bukhārī 1673)
جَمَعَ رَسُولُ اللهِ ﷺ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ بِجَمْعٍ