you can also just bring the context menu up on a addon choose 'addon information' it will bring up a screen where you can uninstall it. be aware that it still leaves a lot of junk in form of dependencies (modules that the addons uses) you will probably begin to see them as orphaned under system/addons. it will also leave the configuration data, so if you install the same addon afain it will have the same config, not to big of a problem I dont know why kodi devs have not implemented an option to delete this to when you uninstall a addon ages ago.