If a MARC subfield is controlled by an authorized value in the cataloging framework, Koha displays the code of the authorized value and not its label, except for certain specific fields (libraries, locations, etc.). Koha should systematically display the label and not the code of the value.
Can you detail which pages/places you mean? For example in the XSLT driven views in OPAC and staff the label will display (or at least it should if nothing was broken) Same for the cataloguing form of the normal editor, where it shoudl display a pull down and the label as well.
I should have been more specific : our use case was a item field, to be displayed in the holding table under the record. Let's say we want to use an authorized value to control the value of "internal note". In the framework for the 995 field (in Unimarc) we can tell that the subfield ($z) must use an authorized value, but in the holding table only the code will be displayed.
OK, I'd suggest making a file specific for this or at least for "item fields linked to authorised values". It will require template changes in lots of places probably to make it work.