I'm using a simple search in the iSearchable integration for FirstName, LastName, etc. and it works fine.

I need to have one more search option such as "AuthCode" and search on multiple fields because the number may exist in one or more fields.

I've tried adding a new option called "Authcode" with the field of "CODEID1, CODEID2, CODEID3" and have tried "CODEID1 OR CODEID2 OR CODEID3" but neither of these actually work.

Is there a simple way to add multiple field names to a search option?

The search options provided by the base of ListX doesn't provide multiple column filters. Not because we cannot extend it, but simply because we generally create a separate search form in that case and simply modify our query according to what is provided in the form. The doctor manager does this type of searching. Take a look.