Thank you for reporting this error. Please could you submit errors like this using the error reporting system in Omniscope and describe what you were doing in the error report, as this will include essential information for us to resolve the problem.
What I was trying to do was to set up a batch output that used a formula field to filter the records. The formula field was calculated in the omniscope session and so it wasn't available to the datamanager and hence the error message saying I was filtering on non-existent field.
One way round this would be to have an "add field" widget in datamanager so that extra fields could be added and calculated at the datamanager level and used for the batch processing - would this be possible?
You should be able to do this using "Field Organiser". With this block, you can add new fields and set formulas which are calculated within that block. Downstream blocks only see the static results of these formulas, unless you enable "Preserve formulas in output".