It’s a feature for podcasters mainly. You can use markers, and save them to wav/mp3 files using “save with all metadata” feature in the export settings. However - they are stored in a different format. The podcast chapters that are commonly used by all podcast platforms are in the ID3 tag of an mp3 file.
When I want to prepare my podcasts I have to use other software to transform markers into chapters.
Like Forecast (only accepts wav files which can be huge, and when they exceed 2Gb app just refuses to work properly), or Auphonic (which is great, but you have to pay for using it when you have a lot of podcasts on your hands... ;)).
It would be awesome if Audition had this feature built in.