How to update metadata of audiobooks in Books app (Catalina and newer)

So...after trying everything, reading tons of posts, here is a method how to change/update metadata like Name of the book, author, track number etc. AFTER importing the book into Books app. As you may have noticed, Books app will recognise the file and refuse to update metadata (except cover art) even after deleting it from library and re-importing it again. The only method I found that is working - except for encoding the file to something else (for example from m4a to mp3), which is a pain and most likely will result in loss of quality - is this:

1) Download Xcode

2) Go to: /Users/YOUR_USERNAME/Library/Containers/com.apple.BKAgentService/Data/Documents/iBooks/Books

3) Open Books.plist (because you have Xcode, it will open plist in a nice plist editor)

4) Search for your book (using Find) and replace all fields you want to change with the new ones. It is quite intuitive so after a minute or so you will know what you are looking at

5) Save it and I recommend to restart a computer

6) Be patient as it may take a little while - even after restart - for the library to update inside of Books app

It is not the most elegant way, but the only way I found that works. Hope it will help someone.