SSAS Tabular Translator

SSAS Tabular Translator is an editor for the JSON translation files exported and imported by SQL Server Data Tools for a Tabular model in compatibility version 1200 or later.

ssas-tabular-translator
You can copy the executable in a directory and run it.
It requires .NET Framework 4. The tool is free and open source.

You can provide feedback in the dedicated issues page on GitHub.