I think it would be nice to have a mechanism / button / actions that remove overwritten shadows and also remove configuration tiddlers if a plugin is uninstalled.
We would need a “registration” tiddler, that defines an “uninstall-actions” with 1 or more filters, that allows the mechanism to remove plugin-specific tiddlers. …
BUT
This functionality will be problematic if done automatically. … Because there may be other plugins, which use the same configuration tiddlers. … So we need to be sure, that there are no side effects.
So for the start it should be a manual process, which is done by the user with UI created by the plugin author. Similar to my remove-states plugin
IMO this addition to the core should be discussed at GitHub, otherwise it will be forgotten.