Frankenstein monster is kinda like Trans folks or people

[Belacqua]

Dysphoria is not gender. It's a disorder. 

If a psychiatrist wanted to find objective evidence for a person's gender, what would she look for? Is this included in the DSM-5?

According to The APA Dictionary of Psychology:

"the socially constructed roles, behaviors, activities, and attributes that a given society considers appropriate for different genders. In a human context, the distinction between gender and sex reflects the usage of these terms: Sex refers to the biological status of being male, female, or intersex, whereas gender implies the psychological, behavioral, social, and cultural aspects of gender (i.e., masculinity, femininity, nonbinary, nonconforming, or other gender)."

So you'd want to look at the person's behavior, much like everything else that a psychiatrist or psychologist is likely to do. Or are you suggesting that a psychological diagnosis isn't objective?

If a person behaves in ways that are traditionally associated with being male, but reports that they are in fact female, what do we conclude? 

Do we even still believe that there are male ways to behave and female ways to behave? Isn't that outdated?

Yes, I believe that psychiatric diagnoses contain a very large subjective element. Psychiatrists can reach very different diagnoses concerning the same patient.