A modern programming language that makes developers happier.

kotlinlang

in idea ultimate i cannot find Diagrams, Generate UML on anything in a multiplatform project
i just installed ultimate to use this feature for a small presentation

That search: <https://youtrack.jetbrains.com/issues?q=UML>
returns this open issue which you can star: <https://youtrack.jetbrains.com/issue/KT-9937>

I think you should add a comment to request multiplatform support, and specify that you installed Ultimate only for that, then realizing it was not supported.