Ok the only thing I'm missing is that I want the "show source code/show definition" I have in IntelliJ and better autocompletion… 😄

There is an open issue about that.

TBH I would be fine using it directly in intellij doesn't really need to be in a notebook

There is an issue for that as well. The problem is that there are different teams working on different problems. Plotly.kt is working fine both from regular idea files and worksheets, but the output is rendered in browser. Currently there is no API to access IDEA inner browser.