MDX Studio

MDX Studio is a tool that was developed by Mosha Pasumansky, a former Analysis Services developer.
This tool is invaluable when writing a MDX query: you have a code formatting feature, an embedded system to analyze query performance and many other features for writing MDX queries.

Unfortunately, the source code is not publicly available and the project is currently no longer being updated by Mosha. Other contributors made an effort to keep the tool compatible with newer versions of Analysis Services and client connection libraries.

https://www.sqlbi.com/tools/mdx-studio/