Say I have my ‘tv shows’ library configured to use content from multiple directories - and I have my Live TV recordings configured to be written to the ‘tv shows’ library. Which directory do the recordings get written to?
Wherever you tell it to using the Location drop down.

If your library has multiple folder locations then it will be an option to select which when setting up the recording
Ah ha, thank you! That location drop down only shows up once the additional directory is added to the library