What is app plugin?
It is mechanism extending application features, so in this case bfexplorer app, without changing existing code.
Your code must implement IBfexplorerPlugin.
During bfexplorer startup are loaded all file assemblies ending with .Plugin.dll and implementing IBfexplorerPlugin interface. It is required that plugin implements WPF UI UserControl so the plugin UI is loaded as document panel.
In my short video I present “My Football Strategy” plugin showing all football matches and for matches already at in-play the match score is updated and when available match statistics is displayed as well.