The MPLAB X IDE user directory (userdir) stores user configuration data such as window layouts, editor settings, menu and toolbar customizations, and various module settings such as the list of known compilers.
When you install plugins (Tools>Plugins), the plugin information (code) is stored in the userdir, not in the MPLAB X installation directory. However, you may change this location under Tools>Plugins>Settings>Advanced by selecting “Force install into shared directories” from the “Plugin Install Location” drop down menu.
To find out where your user directory is located, select Help>About and find the path next to Userdir. This information is created and managed by MPLAB X IDE.