This, I think, is in line with your own suggestions ("'monitoring member" or "lead statutory auditor").

According to the RAE's Diccionario de americanismos, "fiscal has the following meaning in Honduras, Nicaragua, Costa Rica and Bolivia:

"Persona de la junta directiva de una asociación o institución que se encarga de fiscalizar las actuaciones monetarias y las acciones de los miembros."
https://www.asale.org/damer/fiscal

I think it's very likely that it means the same thing in your context in Venezuela as well.

"Fiscalizar" means oversee or supervise. It quite probably includes "actuaciones monetarias", which would match your suggestion of "auditor", though I don't think the role is confined to auditing. To my mind the term that best expresses the range of functions such a figure would perform is "Supervisory Officer". In many difference contexts, a supervisory officer is there to make sure things are being done by the book, as it were. Naturally, in the event of disciplinary proceedings, that person would be involved, but not only or even primarily in that event.

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Note added at 11 hrs (2024-09-06 08:10:39 GMT)
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It is worth nothing that in the document Phil Goddard has cited in the discussion area about the Colegio de Psicólogos of Caracas, "Tribunal Disciplinario" and "Fiscalía" are two separate sections, and the Fiscal Principal, Eliana Beomont Vargas, is not even a member of the Tribunal Disciplinario. This would surely be inconceivable if the Fiscal Principal were the Disciplinary Officer.

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Note added at 12 hrs (2024-09-06 08:24:16 GMT)
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In short, "fiscal" sometimes has nothing to do with its most familiar meaning of a prosecutor, and I think this is such a case.

"Officer", of course, is not a military term here at all. It simply means "one who holds an office of trust, authority, or command", like a Chief Executive Officer, Chief Financial Officer, and so on, in a company.

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Note added at 12 hrs (2024-09-06 09:01:27 GMT)
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"Fiscal", as a noun, very often means a prosecutor:
"2. m. y f. Persona que representa y ejerce el ministerio público en los tribunales."

But it can also mean someone who keeps check on and denounces others' actions:
"3. m. y f. Persona que averigua o delata operaciones ajenas."
https://dle.rae.es/fiscal?m=form

and more specifically "Persona de la junta directiva de una asociación o institución que se encarga de fiscalizar las actuaciones monetarias y las acciones de los miembros", as already quoted above.

I think there's no doubt that it means the latter, not the former in this case. The idea that a medical association would have a figure approximating to a prosecutor seems to be entirely implausible.

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Note added at 13 hrs (2024-09-06 09:22:58 GMT)
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An alternative that has just occurred to me is Chief Compliance Officer.

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Note added at 1 day 10 hrs (2024-09-07 06:16:29 GMT)
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Hi Rodrigo, I don't think you need to worry if you used "Disciplinary Officer" in your translation. It is pretty close, and there is some room for debate about what the term actually does mean. I thought "Supervisory Officer", or "Compliance Officer", which would be my choice, were probably closer, which is why I posted another answer, but I can't be entirely sure. Choose the answer you think is best.

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Note added at 1 day 10 hrs (2024-09-07 06:17:07 GMT)
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Pardon the bold type: it was not intended.