Matroska files have been supported natively since 0.9.6, tag writing included.
This is a lesson to all foobar users, especially new ones: really install only things that you really use. If you install something just to test it and it turns out that finally you don't use it - simply remove it. Foobar has loads of plugins. Searching for them extensively, you can easily reach TLS slot limit. For those thinking about "what has TLS to do with foobar plugins?" - no, it is not about Transport Layer Security. It is https://en.wikipedia.org/wiki/Thread-local_storage .
and third party components can easily use dynamic linking too without worrying about user having to install runtimes or bundling huge additional runtime dlls.