We’ve not had a chance to look at opening up the option for new BS codes to appear on sales invoices as yet. Although it is still something we’d like to address.
You can re-code certain postings made to the BS that are attributed to non-system codes. For example you should be able to re-code between those custom accounts you created. If you are having a problem elsewhere let me know.
EDIT:
@bostin we’ve now added an option that you can access by clicking on the settings icon for a particular nominal account. This will now allow you to mark particular nominal codes as “Purchase codes”, so they can then be utilised within the new purchase invoice screen.