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