I'm not seeing the sort of unlawful "class-based" discrimination that is handled by DFEH. The discrimination that you are being subjected to is the base discrimination applicable to all persons under the Constitution -- i.e., that all laws/regulations must be reasonably related to some legitimate government interest. Laws must be rationally based -- not arbitrary or capricious, i.e., enacted simply because someone thought the law/regulation a good idea.
This is an extremely high bar to overcome -- however, it is not an impossible bar. Your facts suggest that the regulation concerning your promotion has no rational basis, because you could be in charge of managing every government asset in the state, worth hundreds of billions of dollars, and yet not entitled to a promotion, because you did not manage anyone else. I'm making this extreme argument to show how a regulation prohibiting promotions solely because the person seeking promotion does not manage any other person is an absurd standard, considering that you do manage a huge number of vital government assets.
In giving this additional thought, I see (rather than a writ of mandate action) a viable civil action under federal law (42 U.S.C. § 1983), which also has a one-year statute of limitations in California.
You won't be able to process this through any state agency. You will need a private civil rights or employment rights lawyer with some courage. You might even consider contacting the ACLU, though it's really not in their core 1st Amendment area.
Hope this helps.
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