Hi,
ever since my DAX statements got more advanced, I found the code window in Power BI Desktop too small and wanted to use Notepad++ for it. Alas, there is no pre-defined syntax highlighting for DAX. So I went ahead and created my own. I share instruction on how to do that and also the already prepared XML file for easy import into Notepad++ over here: www.sascha-kasper.com/dax-syntax-highlighting-for-notepad/
You can have DAX syntax highlighing inside Notepad++ within 1 minute after reading this.
I hope it helps you as it helps me.