It looks like this is painful and per language, no simply just copy all the translations over. It looks like the process is different for strings and posts/pages too? Resources https://wpml.org/forums/topic/exporting-all-translation-complete-translations-to-transfer-other-wp-site/ https://wpml.org/forums/topic/transfer-my-translations-from-one-to-another-website/

2019-11 We asked WPML Our question Are all translations stored in po/mo files which we can copy using ftp, or are they stored in the database? Answer from WPML Hi Adam, there are 2 big areas but both require database access to some extent: 1) strings in themes and plugins: these are stored in mo/po […]