This repository is no longer maintained, but you are free to fork and maintain it yourself. A better syntax experience is available using treesitter in neovim, using something like tree-sitter-mermaid

Vim Mermaid runtime files

This is the development version of Vim's included syntax highlighting and filetype plugins for Mermaid. Generally you don't need to install these if you are running a recent version of Vim.

How to install

vim-plug

Include the following in the vim-plug section of your ~/.vimrc:

Plug 'craigmac/vim-mermaid'

License

Copyright © Craig MacEachern. Distributed under the same terms as Vim itself. See :help license.