Hi, I have a question. I don't use traveller much so I don't know most of its options. I have a family that has 5 grown-up sims. I want to move out one of the daughters and make her live in another country. You know one of those cool single aunts who live abroad. Is it possible to make her live in France, but play with the rest of the family in their hometown? So she would have a grey icon in the relationship panel like sims you meet on vacation and be able to invite her for 3 days just like foreign friends. But I want her to remain in the family tree and have a sister relationship with the rest of the family. I won't play her btw

Yes, you can move a sim to a new world of your choosing, and they'll function as any other foreign sim would. You need to be in the destination world first, either with the sim you want to move or with another sim or household. For the former approach, you can use the Change Hometown process described here:

Traveler-FAQ#Is-it-possible-to-switch-h ... ermanently

For the latter, take your active sim(s) to the destination world, click on the house where you want the other sim to live, select Add Sim, filter to Homeworld and then that sim's homeworld, and choose the sim from the list.

In either case, keep a backup save from before you try this in case something goes wrong. And travel back to the destination world, even if you don't plan on saving your progress, to make sure the process worked on both ends.

A sim living in a foreign world won't progress the way sims do in the homeworld. Foreign worlds are in a state of suspended animation, and while you can set Traveler to perform a few story progression-like actions the next time you load that world, it isn't the same.