Running the report CVI_CHECK_VISIBILITY_VENDOR confirmed my guess regarding the reason why a field group wasn't displayed in a vendor master (LFA1-WERKS), though the customizing (Cross-Application Components / SAP Business Partner / Business Partner / Basic Settings / Field Groupings > Configure Field Attributes per BP Role) was showing this field group as not specified (meaning displayed, if I'm not mistaken): the customizing for the vendor group (Financial Accounting / Accounts Receivable and Accounts Payable / Vendor Accounts / Master Data / Preparations for Creating Vendor Master Data > Define Screen Layout per Company Code (Vendors)) had 'taken the lead', so to say (though the field was hidden in the FLVN01 BP role, general data, 'Vendor: General Data' tab, while the field LFA1-WERKS was marked as suppress in the 'FI customizing' in the group for the vendor, purchasing data > additional purchasing data).
Nevertheless, before running the report, I thought that the guess I had was wrong: when comparing to the system where the data where copied from, the one where the field in the vendor master was visible and ready for input, I didn't see any difference, meaning that the field LFA1-WERKS was also marked as suppress in the 'FI customizing'.
One of the differences in that the 'master system' is a S/4HANA 1809, when the other is a 2020 one and most of the components have then different versions (like the S4CORE, the CA Component, the BC one, etc).
When running the BDT Analyzer in my vendor master to see the status of the field group (OK code BDT_ANALYZER in the transaction field when in the BP), I noticed that the CVIV16 section (sub-section in the main one CVIV22) is labelled 'Customer: Plan' in the 'master system' (...) when it's called 'Supplier: New Plant' (new?) in the target system.
Anyone knows if that technical difference in the SAP release is the only reason for the issue I have?
Thanks in advance :)