How can I keep my interface translations separate and upgradable?
I need to keep my own translations of some parts of the Plone User interface. How can I keep these separate from the Plone translation files, so they don't get deleted when I upgrade?
Put your translations in a separate .po file with the domain plone in the header.
This way, you will have a mytranslations-xy.po with your own translations that will be added to the Plone translation name space on load, and you can update the normal plone-xy.po files without affecting your translations.
If you keep your files in a directory called i18n in your INSTANCE_HOME directory, they will always have priority over the ones shipping inside Products.