I worked as a Smalltalk developer for a few years, and it spoiled to such an extent that I’ve tried to make an extension for IntelliJ to replicate the browser for Java development. Maybe I should revive that project, actually…

Please do. I would love it for Python and TypeScript as well. It could use data from where the "Structure" pane gets its contents

How about the Spyder IDE for Python? https://www.spyder-ide.org/