UDF in Cost centers table

Hello experts

Thanks to the invaluable assistance of the people in SCN forum, I have been able to develop a solution intended to block postings when a budget for a certain project is going to be exceeded.

Solution consist on a couple UDFs in OPRJ table, one for specifying the project limit amount and the other contains a FMS with a query with calculates the cumulative amount for the project in purchase invoices (PCH1). And a couple queries in TN, one is intended to update the cumulative UDF automatically each time a purchase invoice is posted, and the other query is the one which blocks the invoice postings in case the posting is going to cause a project budget overrun.

I have a requirement to develop a similar solution to this one, but applied to cost centers in this case. I though first that it was going to be quite easy, as it seemed that it was only needed to adapt the queries and create the UDFs in cost center table. But the problem is that when adding the UDFs in UDF Management > Costing > Cost center category, I do not see a way to edit these fields. I can see them by using the search functionality in "Cost center- setup" form, which leads me to the list of Cost Centres, and activating them in form settings, but I haven't found a way to edit them, so I can set the FMS in one of the fields and update the budget limits in the other one.

Thanks and regards