From OpenSCADAWiki
To store the translation of such messages, a separate container-table "Trs" is specially provided, which is located in the database-storage associated with the OpenSCADA object with such procedure. Messages wrapped with the "tr()" function are included in the "Trs" table at the time of this procedure execution or compilation, for string literals, and these messages in the procedure themselves must be the BASIC language. 
At this time, it is not possible to track changes of messages wrapped in the tr() function, so they will all accumulate there, but you can delete them manually from the manager context menu.