[Are the regular sunnahs (rawātib) recommended during travel and when combining prayers?]

Answer: What is reported from the Prophet’s practice is that when he combined two prayers—whether in travel or at home—he did not perform supererogatory prayer between them.
There is also a report that the Prophet (may Allah bless him and family and grant them peace) urged performing the two rakʿahs of Maghrib and of Fajr in both travel and residence.
Yes, the two reports can be reconciled by restricting the hadith by reference to his practice: the meaning would be, “Do not leave the two rakʿahs of Maghrib in travel or at home unless you are combining.” And Allah knows best. On this basis, the regular sunnahs are recommended if the worshiper is not combining two prayers; if he is combining, then they are not recommended—whether the combining is in travel or at home.
As for the two rakʿahs of Fajr being a sunnah in travel and residence—there is nothing opposing that, and the Messenger of Allah (may Allah bless him and family and grant them peace) prayed them on a journey the day he and the Muslims overslept Fajr and were not awakened except by the heat of the sun.
Likewise, the night prayer and witr: the Prophet (may Allah bless him and family and grant them peace) used to pray them while traveling on his mount, as is well known.
The real point of discussion is the two rakʿahs after Ẓuhr and after Maghrib.
Source : Min Thimār al-ʿIlm wa al-Ḥikmah vol.1