Considered an "irreversible decision" during Job Cost Setup, in your existing data file that format cannot be changed after the format has been set and the Job Cost Master file is created.  I think you could create a new data file and make that change before starting over.  Ugh!   There is also info about Sections in JC Help and from Knowledgebase.  Maybe this will help you go another route:  https://support1.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=48881&sliceId=1&isLoadPublishedVer=&docType=kc&docTypeID=DT_Article&stateId=37985&cmd=displayKC&dialogID=1609439&ViewedDocsListHelper=com.kanisa.apps.common.BaseViewedDocsListHelperImpl&openedFromSearchResults=true

Have you done this for your company? 

I believe Sections are available if you have PJ.  We do not have PJ so I couldn't give you more direction on that.  Yes, I have started the company over one time.  It was long ago and it seemed like a lot of work.  They have a tool under "Options" to make a new company.  I remember it wanted to do GL Prefixes which we don't do so the work around was different, but I don't remember how.  Also a consultant may be able to help you.  I remember resorting to one because the setup had too much work to do timely.  They were a great help.  Once I had a clean, brand new Data Folder, I copied it.  I always upgrade it.  So it could be copied to a new data folder to start over if something happens and that's what we need to do.

A consultant may also know of a work around for the cost code delima.  You should call yours and ask before doing all the work of a new data folder.