Using Odoo 13 enterprise on premise, I tried hard to change the German translation of the LOG button in the "Leave a note..." page of the chatter. It is "Protokoll", which is not quite correct, since the verb "to log", so "Protokollieren" or better "Notieren" is meant.
I changed the translation in the po file addons/mail/static/src/js/composers/chatter_composer.js and tried to update the mail module and reloaded the language. The term does not change. I also tried clearing the browser cache. Even odoo-bin -u base --i18n-overwrite made no difference.
Correction: I edited the translation in the file "addons/mail/i18n/de.po", of course.