The only thing I guess a HH Menu that Opens up a UD20 screen for example and then you have dropdown and a button. As Simple as Possible.
You can do this.oTrans.Session.SetPlantID(“12334”); and it will swtich it or even change users in there with .SetUserID(…);
SetCompanyID(CompanyID).SetPlantID(PlantID).SetUserID(UserID).SetEmployeeID(EmployeeID)
If I recall you can even do SetWorkstation - Perhaps just make a Workstation Switcher.