Its not symbolism.
The reason people view Dax as a trans is that they were at times male and at times female. That is not symbolic of being trans, it is just being trans.
However, despite exploring what it means to be a trill passing through generations of hosts, the changing gender aspect of it never comes up. If Kurzon was a women, I doubt we would be talking about Dax as a trans stand-in, but I can’t think of a single plot point or character development that would meaningfully change.
Normally I’m a believer in death of the author, so I won’t be offended if anyone wants to completly ignore thus section, but in the DS9 documentary, they have a section on LGBT representation, and their big example for it was Jadzia. However, that was not for being trans, it was for being in a gay relationship.
To be clear, the target of the shooting was an unidentified individual, and a scoped rifle was found in the vicinity.
Maybe something else happened, but it looks like the secret service doing their job and stoppingva shooter before he was ready to take the shot.