The transgender censor seems to be simple string matching (if query == "transgender"). Just putting the forbidden word in quotation marks makes it searchable, too [1].
I wonder if the filter was intentionally implemented in a shitty way by NIH staff so that they formally comply with an internal order but offer easy ways to circumvent it.
https://search.nih.gov/search?utf8=%E2%9C%93&affiliate=nih&q...
Adding an extra word to censored searches appears to defeat the effect for now. For example, “diversity” is censored but “diversity a” works.