Optional Items and Add-Ons are a YouLi feature that allows you to make Itinerary Items opt-in for your travelers. When you create Optional Items and Add-Ons you can also decide if you want this item to be defaulted to selected when the traveler registers. In other words, do you want this item to be automatically selected for your traveler when they register for you trip?
To turn this feature on you need to check the box 'default to selected when a traveler registers' within the Highlight or Itinerary Item you are creating.
For example, do you carbon offset your trip for your travelers? Do you have an optional airport transfer that everyone always chooses? Now you can have that optional item default as selected when the traveler registers.
Note: Once selected, this is only automatic when your traveler registers themselves onto a trip. If you are manually adding travelers or bulk uploading travelers then you need to also manually add the optional item by going into 'VIEW AS' and adding them item for them.