As of v2.3 of the Jomres plugin manager, third party developers can now add their own tabs to the Jomres plugin manager.
The idea is that you would include a copy of this script with all of your plugins. This means that you will not need to override the showplugins minicomponent in your own extensions.
The script is a simple example showing you how to structure data which is returned to the plugin manager. The key part is this line
$this->ret_vals = array ( "TAB_ID" => "testty" , "TAB_NAME" => "test" , "TAB_CONTENTS" => "tab contents") ;
The TAB_ID is to allow the tab to actually work. It's a basic html id attribute.
TAB_NAME is what will show at the top of the pages, in this example it's hard coded but you could use jr_gettext(.... too for creating multilingual content.
TAB_CONTENTS here is again hard coded, for simplicity. In reality you would probably want to make one or more Guzzle or CURL calls to your own server to an endpoint or page with details of your plugins ( including versions ). This gives you then the opportunity to highlight to your users if there's an update to your currently installed plugins, news about new plugins that you have created, etc.