The Classic Custom Fields feature was the initial version of custom fields in Manager.io. We advise against using classic custom fields and recommend adopting the new custom fields instead. For more information about the new custom fields, see the Custom Fields guide.
To convert your classic custom fields to the new custom fields, click the Upgrade button located at the bottom-right corner of the Classic Custom Fields screen.
For more detailed instructions on upgrading, refer to the Upgrading Classic Custom Fields guide.