I'm trying to create a saved search that shows me who created which record - for opportunities, quotes, and sales orders. Does anyone know how I could show the "set by" field in a search so that it shows the earliest system note and not the latest? I can see the "set by" field as an option under System Notes, but not any variation of it.

Do you have the last sales activity bundle installed? It should have the "created by" field created for you.

Yes, but it does not have that field.