Finding the Most Recent Record Updater
Use the dense_rank function in a formula to order records by values in a field and assign each record a consecutive numerical ranking from 1 to n, where n is the number of records returned.
Use the keep (dense_rank) function to return only the first or last ranking record as ordered by values in a specified field.
For example, to return the name of the user who most recently updated a document, do a document search and create a Formula(Text) field with a Summary Type of Minimum and a formula like the following:
min({systemnotes.name}) keep (dense_rank last order by {systemnotes.date})