Often there are several language variations, with only minor differences, within the same project, e.g. English, English US and English UK.
Instead of copy/pasting the translations, as you update one of the languages set up auto-fill rules in order to perform automatic updates.
Create rules by navigating to project settings > Language auto-fill.
Select a language to monitor for changes (source language) and one or more languages to auto-fill to (target languages).
Enabling the Set Unverified on update switch will mark the automatically updated translations with an Unverified flag so translators can easily filter out and post-edit these items.
By default the system will only update empty translations in the target languages, however you may enable the Override flag to automatically fill in items that already containing a value.
You can set up multiple rules for different language pairs by clicking the Add another rule button and repeating the setup.