If you have multiple glossaries in Transifex and you want to merge them, please follow the steps below:
Go to your Glossaries from the main navigation
Download each of the glossary files that you want to merge into a master glossary.
Click on the gear icon next to the glossary that you chose to be the master glossary.
Upload each version of the CSV glossary files that you downloaded in step #2.
Make sure to keep the “OVERWRITE EXISTING ENTRIES” disabled, because you want to keep adding the terms from all these different glossary files that you’re uploading. Otherwise, you would overwrite the existing glossary with the file that is being uploaded.