I created a Zed extension for Apache FreeMarker templates with tree-sitter-based syntax highlighting. FreeMarker is a Java template engine that's still widely used in enterprise apps, but modern editor support has been lacking. The extension handles both angle bracket and square bracket syntax, mixed HTML content, and all FreeMarker directives through a custom tree-sitter grammar rather than regex.
GitHub: https://github.com/debba/zed-freemarker
Zed Extensions: Search "FreeMarker"
Built it mainly for my own projects, but figured others maintaining legacy systems might find it useful.