Hi,
when adding a Sims to another lot with MasterControllers Add Sim option, while being on vacation removes the vacation bar and the travel home interaction etc.
Does that option do the same thing as Chnage hometown or does it not run all scripts and will break the game?
I reloaded an earlier save just to be sure I did not break anything.

You are using Add Sim on your own vacationing actives? Then yes, I could see where everything would break. Add Sim is what changes a sim's "permanent" home, not a vacation home, and as far as I know it is not capable of properly shifting out of vacation mode into regular homeworld play like Traveler's Change Hometown is.

I add sims to my households on my vacations all the time but I use the EA 'ask to move in interaction' - and then use 'fix homeworld' when I get back. This has worked well for me for about 20-25 sims so far.

The question as I was reading it was about using MC > Add Sim on a sim/household that was already active and apparently not intending to ever go back home, not about adding new household members. But maybe I was misunderstanding?

Hm, they said they want to travel home so I assumed they wanted the vacation to end. I guess we'll have to wait for KittyTheSnowCat to come back and tell us!

But I could be misreading too, wouldn't be the first time...

I sounds to me like KittyTheSnowCat is trying to remove an active sim from the active household and place in the inactive population of a vacation world via the Add Sim command. Then have the active household travel home. I've always wondered if that would work but have never tried it. I could be wrong about the question though; I don't fully understand the situation or what KittyTheSnowCat is trying to achieve.

I traveled one of my students back to the town her family lives in (I don't use EAs Uni so I just traveled her from her homeworld to a world where her husband and kids are living). I wanted her to plant something at her home, but she couldn't because she was just visiting so I added her to the household with add Sim. And then I realized that it removed her traveling status.
Does anyone know a clever workaround to having her visit her family and actually being able to do the laundry and plant plants without having to use Change Hometown and reloading? IS there any Mod that enables planting off the homelot?

Tempest allows planting off the home lot. Place the harvestable on the ground, click on it and choose the 'plant here' interaction. I don't know if that works while a sim is on vacation though. You might also try 'moveobjects on' then planting from inventory. I use that to plant indoors. Does she own a vacation home in her family's world? I haven't had trouble growing things in Egypt while my sims were living on their vacation home lot there. Maybe have her purchase a small empty lot nearby as vacation home to plant?

Also, did you try setting Traveler's 'treat as vacation' to false? I haven't ever used that setting, I'm not sure what it can do.

I have no idea about the laundry.

Problem is that she is basically a guest. The game has her live in the base camp, but I wanted her to plant at her families home.