I downloaded a plugin from a plugin platform, and some of its features are of interest to me, so I want to debug it. I downloaded and successfully ran the IntelliJ Community project. Now, how should I debug and analyze this plugin?
If the plugin is open-source, grab the sources, compile it and run (in debug mode) the plugin in a sandboxed IDE. You can also enable the internal mode of the IDE, then use the UI Inspector. Everything is explained in the docs. Finally, https://plugins.jetbrains.com/intellij-platform-explorer/extensions can be very helpful.
If the plugin is closed-source or under copyright, you probably don’t have the authorization to de-compile/debug it, so we won’t help you ^_^.