Gesehen habe ich das auch noch nicht, aber vermute "männlich/weiblich/divers" nachdem es zuletzt ein Urteil des Bundesverfassungsgerichts gab, das vorschreibt eine "positive" Bezeichnung für die zu ermöglichen, die sich weder als männlich noch weiblich definieren.

Das steht für "divers", also für diejenigen, die sich weder als männlich noch als weiblich definieren

"The plaintiff had applied to be officially registered as “inter/diverse” or simply as “diverse”... "

Consequently I could use (m/f/i) or (m/f/d). But most sites I have visited (such as the Intersex Society of North America, a spokesperson of which was quoted in the FT article) use the term "intersex"; I didn't find the term "diverse" used specifically much at all in English-language pages.

In a paper from Northwestern University School of Law

(https://www.google.ca/url?sa=t&rct=j&q=&esrc=...)

I found a reference to "male/female/other", which also sounds like a good potential translation: "(m/f/o)"

The "(m/f/o)" variation seems the best to me.

I have found a number of sites with "Equal Opportunity Employer M/F/O/V" or "EOE M/F/O/V" on their job vacancy listings.

I have not yet been able to find a site that clearly specifies what "M/F/O/V" means, but I assume it means "male/female/other/?" -- but if I am correct in my assumption, I still can't figure out what the "V" might mean....

Here's an article here about preferred usage for job advertisements:

"SO" is sometimes used for "sexual orientation"

But how about using "M/F/X" where X is the non-binary, gender-neutral international marker now used for some passports, IDs etc.?

"We can issue a passport to sex and gender diverse applicants, identifying them as M (male), F (female) or X (indeterminate/intersex/unspecified)."

"Canada introduces gender-neutral 'X' option on passports"

"Canada becomes the first country in the Americas to allow its citizens to use an “X” category, joining those in Australia, Denmark, Germany, Malta, New Zealand and Pakistan."

"Until now, state IDs in the US have only given two options for gender: “M” (male) or “F” (female). The new policy from the Oregon DMV would allow people to select a third, gender-neutral marker: “X” for “unspecified.” This provides a new option to people with different or no gender identities, or those who simply prefer not to have a gender listed on their ID."

Yes, you are correct, it was EOE M/F/D/V!

The sites I found as references were books.google links and the views I had were slightly small; when I enlarged them I realized that what I thought was an "O" was a "D". But even though I was mistaken, the fault lies partly with google, because if you do a search for the following text, the hits which attracted my attention on the very first page actually read "M/F/O/V", even though on the actual books.google page one finds a D (a google scanner error perhaps...?):

"m/f/o" job vacancy

As for "M/F/X" there certainly seems to be quite a lot of hits in google for that. The majority of them seem to be concentrated in sites originating in Belgium. Nevertheless, I think I will go with "M/F/X", because it seems to be in use in the job adverts of some major organizations, such as BNP PARIBAS.