First: is the list a good place for a documentation request?

This is about metadata_lock_info plugin:

https://mariadb.com/kb/en/metadata-lock-info/

I hope I'll see documentation about the possible values of LOCK_MODE and LOCK_TYPE columns. The latter column may seem ovious, but it is not: when are such locks acquired/released, what kind of operations are put on hold?

Regards,
Federico