Chris Webb puts the pieces together for us:
For me the biggest new feature in the January 2025 release of Power BI Desktop is the new TMDL View; many other people like Marco are excited about it too. For more advanced Power BI developers (and honestly, I don’t think you need to be that advanced to get value out of it) it makes certain editing tasks for semantic models much simpler, and while I won’t be abandoning the main Power BI Desktop UI completely or stopping using external tools like Tabular Editor it is something I see myself using on a regular basis from now on.
Click through to see one thing you can do with it.