What is the intended use of the Internal Solicitor field on Transaction, which is a lookup to User? Is there any automation that is supposed to populate this field? It isn't on the New Gift Interface VF page.
The Internal Solicitor field on the Transaction can be used to indicate whether the Transaction (gift) was a result of another person's fundraising effort. No, there is no automation behind this field. It may be better to use Soft Credits to give recognition to another individual's or organization's fundraising effort.
You can add/remove fields from the New Gift Interface VF page through Field Sets.You can find instructions here.