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@ruggercsc, I'm partial to "Grand Poobah". Have you considered "
Special Projects", "Special Forces, GSDO", or "Kicker of Assess, Taker of Names"?
In all seriousness, you should check with your supervisor first. Chief has varying connotations and responsibilities depending on the agency. I typically see it used to describe supervisory positions at the GS-14 and 15 level, but I've also seen it used as high as ES-1 and EJ-3.
There is no OPM standard for titles. It's left up to the discretion of the agency. One's title cannot be a factor in assigning a grade to the position wrt desk audit.
Your safest bet is "Supervisory Engineer" or "Supervisory General Engineer". You can add " , Engineering Services Branch" as applicable depending on the style guide for your business cards and email signatures.
"Chief Engineer" "Engineering Chief" without any other language or modifiers tends to be reserved for pretty high levels. They're often written into the regulations governing conduct, operations, and authorities within the agency. The unauthorized use (again without modifiers) could get you into serious ethical and legal trouble.