You should prioritize your strongest skill, or the one you want to be hired for most. If the majority of the work you want to do on here is developing, you could even ditch the assistant role in your title. People like to hire people who seem like they are especially specialized.
That said, my profile is a terrible example. If you want to include both, instead of a vertical bar, I'd use 'and', '&', or a comma.
re: "Okay so whats the right way to put in job title when you are a developer who also work as a virtual assistant"
You shouldn't be working as a virtual assistant.
Or at least don't advertise that you are.
I have hired over 80 freelancers on Upwork. Sometimes I hire people for very specific technical expertise.
One of the main ways I decide who to hire is that their job title focuses on the technical expertise I need.
So if I see these three people:
- Ubunutu expert
- Ubuntu expert / virtual assistant
- Ubuntu expert / voice-over artist
...I would probably hire the first one and not even look at the profiles of the other two.