Unfortunately, you will not be able to increase the number of fields in the header. PPM limits the number of custom header fields to 50. You will need to either add the field to the details section or move one of the other custom header fields to the details section. If you choose to move an existing field, you will need to reset all the status dependencies for that field and if it currently has data, you will need a script to move the data and clear out the old data. Also, if you move a field, make sure it is one that is not in both the proposal and project, otherwise this data will no longer transfer when the project is created.
The header table has a column for batch_number but it is always set to 1. So it looks like HP could implement this in the future by adding this selection and modifying the code to use the batch_number to identify which group of 50 fields is in use. I have not checked, but I would bet that this has already been submitted as an enhancement request.
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