Localization workflow for updating development language

Question

I have a project where I've setup localization using NSLocalizedString with keys instead of actual values for text parameters, i.e. something like this:

NSLocalizedString("RunningDistance", "distance for a marathon")

instead of this:

NSLocalizedString("Running distance.", "distance for a marathon")

Then, I exported them to xliff for translation and imported back; and it's all working. Now, I want to add new strings (and lots of them).

I read that it is currently not recommended (and supported) to use genstrings for swift. I thought I should export the development language to xliff, add translations and reimport. I tried this and I get the The XLIFF file does not contain a target language error.

1. Does this mean I need to add all those strings manually into Localizable.strings and elsewhere (as I'm using base localizations)?

2. Is there any other way to get this done, and import my base language xliff?

Lobe