It is an export function that is required to load music onto a USB stick in order to play in your car. I simply use Microsoft Media Player on PC.
Some caveats:
I have yet to find a car that recognizes the playlist. Even though a Chevy vehicle I tried had playlist capability it did not see the playlist file I created.
Every car I tried recognized and played the .wma files - they all played them in the same order and the car media systems put artists in folders on their own. Car mfg dependent on how the music you provided is presented. Expect none of them to be identical.
Have not seen a car media system that has a "random/shuffle" way of playing files, which is really what is needed.
The 192/24 files I play in my car really shows how much better the source is to the system that you are playing them in. In other words, it is a bit disappointing when I play them in the Chevy or Fords I drive at work. Those stereo systems are just bad and your high definition music shows that off, although it sounds better than any other source you may use in those systems. My Mazda is Ok. What you really need is a great stereo in order to play high resolution files (duh!), and car stereos are generally not up too task. I would expect better results in higher end cars, but there are no guarantees.
There is NO REASON to utilize anything beyond 192/24 files in your car. FLAC is not going to make your car stereo sound better unless you have an aftermarket system installed. Maybe someone will tell me that their FLAC files sound better in their McIntosh stereo In their Jeep Wagoneer than 192/24, but that would be a reach. That is if FLAC files are recognized by your car in the first place, which I would not deem in any way necessary.
I have over 3 days of music in my Mazda which is great for long trips.
Use a USB like the Verbatim "Store n' Stay" nano which is extremely small and does not stick out of your car's USB port. Don't use a USB with function lights. Put it there and leave it. I used the 16GB version and 72 hours of 192/24 amounts to less than half of the 16GB, if that.