GlotPress plugin that allows to define a project as source of a master (base) glossary.
The glossary for the same locale translation set of that project will be merged with the project glossary.
Add this to your wp-config.php file and change 123 to the id of the project that should be the source of the master glossary.
define( 'GP_MASTER_GLOSSARY_PROJECT_ID', 123 );
Enable the plugin through wp-admin.