How to add additional source fields to a lookup field on a Sharepoint Form?

Question

The advanced settings for Lookup Fields in Sharepoint Forms allow me to select additional fields from the source list to display. However, when I select these they do not appear in my form. The source fields are all of type Text.

Answer 1

These additional fields will never show up in the form, they only show up in the submitted results of the form.

In other words: the person filling out the form selects the main key, and all the other related fields you added will get added automatically when the person submits the form.

Hopefully this makes sense.