Although this information is nominally lost in join there are ways to build the workflow to enable that.
Depending on details you might be able to use the route component to seletively apply the barcode to only certain files before you join them all. That will do the trick in most cases.
If the contents of the barcode contain informaiton that is only available after the file is joined (which is pretty rare in my experience) then you would need a little scripting to capture the information before join (using the external node) and to leverage the captured information after join.
I would need a bit more in terms of details before thinking about a suggestion.
Send me a private message / email with additional details.
I have a workflow that uses the Collect component that gathers multiple CSV files that are a single row though the PDF file being called vary in the number of pages. Collect will gather several CSV files and the ulitmate goal of the workflow is to merge the PDF's all into one print file. The workflow steps are Optimize, Collect, Join, Barcode, Add Leading Banner and then Save. There is a field in the CSV fiie that indicates if the PDF's represented by that CSV file would get a selective insert or not. We want to barcode the entire concatenated file in sequential order, that is why we Join before we Barcode. Would the Selective Insert value still be available after joining all the files or is it lost once we join? If Core is still knowledgable about what the Selective Insert value was in the CSV file for those PDF pages then we are good to go, if not then do you have another suggestion as to how to accomplish this?