SSMS 17.x had notorious issues: random crashes, slow Object Explorer expansion, and memory leaks. SSMS 18.x focused heavily on reliability.
: Visualizations and settings for the new performance-tuning engine. Notable Changes and Removals Database Diagrams : Initially removed in 18.0, this feature was added back in version 18.1 due to high user demand. System Requirements : Requires .NET Framework 4.7.2 or higher to run. Are you looking to sql server management studio 2019 new
If you are still on SSMS 17.x or an early 18.0 build, here is the upgrade path: SSMS 17