Plugins
Plugins let you add exporters and "codeview" capabilities like Mermaid diagrams to the MarkupEditor.
Installing a Plugin within the MarkupEditor
From the Settings->Plugin page, select the + button and add the plugin you want. The list here on the web site gives you an up-to-date view of plugins available from the MarkupEditor.
Creating and Publishing a Plugin
Follow the instructions in the plugins README.md to create a plugin. You can always create and install a plugin privately, but to make your plugin publicly available to other MarkupEditor users, submit a pull request. Once approved and merged into the MarkupEditorApp repository, it will appear here and in the app.