In a Nutshell: Background
The term Umm al-Fara'id is not mentioned by any of the classical scholars, according to my research. If the questioner means whether scholars argue for the importance of Khilafah, or without it many if not most duties could not be discharged, then the answer would be categorically, yes. If he is saying the literal phrase was used by them, then no.
Some people argue classical scholarship claims Khilafah to be the mother of all duties (ِالخِلَافَةُ أُمُ الفَرَائِض). Some people attribute this saying to Abu Hanifah, others to Shafi'i and others to the contemporary Mufasir Ibn Ashur.
But after doing research for these exact words, I found this statement in no classical scholar's book.
I did, however, find a reference for a book published by a Pakistani Hizb Tahrir member, (نَفِيِد بُوت) Naveed Butt, in an article dated 11/11/2014, titled (ِإِقاَمَةُ الخِلَافَةِ هِيَّ أُمُ الفَرَائِض) 'The Establishment of Khilafah is the mother of duties'.
The statement is attributed to Abu Hanifah, however the closest statement I found was his statement in discussing the issue of Khuruj 'Ala al-Hakim (rebellion against the ruler) where he said it is wajib if he is a fasiq and if he does not enjoy the good and forbidding the evil (ya'muru bi-lma'ruf wa yanha 'an al-Munkar).
Abu Hanifah argues this activity is primarily fard and can't be established except by the establishment of the state and so it is not compared to any other fara'id (duties) in terms of importance.
Abu Hanifah's student al-Jasas narrates Abu Hanifah said:
ِوَهَذِهِ فَرِيضَةٌ لَيْسَتْ كَسَاِئرُ الفَرَائِضَ لَأَنَّ سَائِرَ الفَرَائِضَ يَقُومُ بِهَا الرَجُلُ وَحْدَهُ، وَهَذَا مَتَى أٌمِرَ بِهِ الرَجُلَ وَحَدَهُ أَشَاطَ بِدَمِهِ، وَعَرَّضَ نَفْسَهُ لِلْقَتْل
"This faridah (a'muru bi-lma'ruf wa nhi 'an al-Munkar which is entitled by the state) is not compared to any other fara'id, because the rest of fara'id can be established by any man alone but if a man does this alone, he will shed his blood and exposes himself to murder ..." (al-Jasas, Ahkam al-Qur'an, Vol. 2, p. 39)
The concept of khilafah being the mother of all fara'id is however correct, articulated in various forms by scholars over the centuries. Imam Qurtubi for instance cited it as the pillar upon which all other pillars ar built:
"When Abu Bakr was about to die he proposed Umar to be the Imam. No one said this is not wajib on us or you. Rather this indicates its obligation as the Khilafah is the pillar upon which other pillars rest."Conclusion
The term Umm al-Fara'id is not mentioned by any of the classical scholars, according to my research.
If the questioner means whether scholars argue for the importance of Khilafah amongst all fara'id, the answer would be yes. References
Al-Jasas, Ahkam al-Qur'an
Naveed Butt, The Establishment of Khilafah is the Mother of all Duties