When we read the Qur'an and sunnah we may come to the conclusion that a trustworthy witness can be any person who is widely considered as trustworthy and a scribe could be any person who is able to write and read.
And we know that a scribe and two witnesses are necessary for writing contracts and witnesses are necessary for testimonies in many cases which are mostly quoted in the Qur'an.
In many Arabic countries there's the so called job of a al-Ma'dhun (spelled al-Ma'zun in Egyptian Arabic) المأذون -literally the authorized- or Al-'Adel العادل (plural العدول al-'Udul) in Morocco (AFAIK) -referring to trustworthy witness as stated in for example 2:282- these parties usually play parts in case of at least as far as I know marriages (for the Ma'dhun) and would write the contracts and play the role of the witness. Al-'Udul in this case may always come in pairs so that the two necessary witnesses for marriages or for any other contracts would be present.
Both the 'Adel or Ma'dhun are nowadays assigned by the ministries of justice in their countries and send their reports/contract copies to the local courts.
Based on my above quoted facts the fatwa islamqa #813 comes to the conclusion that the presence of official witnesses is not necessary if all conditions for a valid marriage are met, but it doesn't seem to consider this job as an innovation or anything which seems to be considered new to Islam. And I can certainly find benefits in such a profession. Especially when these individuals are trained and have knowledge in both contracts in Islam and testimonies. Which at least seem to apply to the profession of a 'Adel as quoted above.
I wonder when (and where) this job was first introduced and established in Muslim societies?