Can players gain additional types of duty as they progress or are they limited to the ones they started with at creation?

That really depends on your gm and how they view such additions?

For me I'd ask how your new duty relates to your old one and what you've done to merit that addition.

Worst case scenario maybe you halve your existing Duty score to add that other one by the same amount you lowered your first duty or replace it entirely, but there still needs to be a reason this happened.

How has others handled this?

I'm the GM!

Thanks for your suggestion!

Since characters can start with multiple duties as-is I don't see why it couldn't happen during play. It would really come down to the character's narrative - why is this thing now important to them - much like motivations.

The new one would start at 0 though. Duties don't have to have matching values and the values represent what you've already done in that role.

I give my players the option of changing their Duty every time they reach a new Contribution Rank. Most don't change, but I feel like that's a good time thematically.

Hadn't considered the idea before, but this could be a good way to show what a higher effective rank in the rebellion (or empire) would mean. The higher you get in anything the more responsibilities you are expected to have, though it would need to fit into character narrative and what is actually happening.

I wouldn't let them have more than two, though, and I'd restrict it to maybe one or two players at a time. Otherwise a group of "clever" players could game the system pretty hard.

I like the idea of swapping new Duty for old. Let's say, for example, that a party contains a Wookiee gladiator. At first, this character's Duty might be Combat Victory. During a scenario involving the liberation of Wookiee slaves, however, the character finds a new purpose, and decides to take on Recruitment as a Duty.

-Nate