Hello @Pedro_Bernardo_Juan_Celis_Caraballo ,
I think there are a couple of reasons why you can’t do that.
- if a user would be allowed to do what you want, a malevolent user could keep on submitting new entries and pollute your lookup list.
- the way the forms are loaded, don’t allow easy work arounds, because the lookup list becomes static upon loading a form.
If you insist on having new entries, I described a workaround here. You could enhance the work around with admin approval if you would like to do that. Generally speaking, I don’t think it is a good idea to have not-logged-in users making changes to lookup lists in forms