mkdx is a Vim plugin that provides a comprehensive set of mappings and functions for editing Markdown files. It handles list insertion, checkbox toggling with hierarchical state updates, header promotion/demotion, text wrapping (bold, italic, code, strikethrough, links), CSV-to-table conversion, dead link detection (fragment and external via async curl), table of contents generation (including nested `<details>` tags), fenced code block insertion, quote toggling, and enhanced `gf`/`gx` navigation. The plugin is highly configurable through a single `g:mkdx#settings` dictionary with runtime validation and auto-update via `dictwatcheradd`. It includes a full test suite using Vader.vim and supports both Vim and Neovim. The architecture follows standard Vim plugin conventions with `plugin/`, `ftplugin/`, `autoload/`, and `after/syntax/` directories, demonstrating advanced Vimscript patterns such as asynchronous job control, deep merge of settings, and dynamic syntax highlighting.