Currently, I'm trying to install an MPS plugin manually. "Manually" means outside the MPS by placing files in a proper dir. I'm trying to use not the MPS installation dir but the user MPS files. For example, I read this information about the plugin directory: https://www.jetbrains.com/help/idea/directories-used-by-the-ide-to-store-settings-caches-plugins-and-logs.html#plugins-directory
But the problem is that if you simply put the plugin to the user plugin dir nothing happens. Also, if you delete a plugin from the MPS IDE the plugin still exists in this plugin dir. It means that MPS do something additional to really install/enable plugins, but I can't find a solution.
I would like to ask any hints about how to install plugins not from the MPS IDE if it's possible. Thanks.