To update the metadata of a document that is stored in a folder (or a subfolder of a folder) in a library, we use two events in the right order.
First we use a Search Event to find our document in the library. The trick in our case: we search by the ID of the document, because we do not know in which folder we have to search.
The result of our search is stored in a Content Field. By default, we can only find one document, because the ID is unique in the library.
The second event is a SharePoint Documents event. The action is configured to Update Document’s Metadata of a document. To find the document, we use the members FolderURL and Item of the content field, we have filled in the previous step.
In the Document Metadata part of the wizard we assign the values we need to set for the document.
This method for updating metadata could also be used, when the document is stored in a document set.