@Joseph-TP to clarify, the USB storage support in tp-link routers consists of TWO interfaces:  One is the file system support and that is where Samba is used.  This allows discs hanging off a network to mimic local discs.  All file system operations are supported: creating files and folder, reading files, getting contents of folders, writing files, removing files and folders & etc.

The Second interface is the one I have questions with and that is the Media Sharing interface.  This is where DLAN support is.

Can you please focus your reply to my issue on the Media sharing interface?  Not on USB storage in general, or the filesystem interface.  I need help with the DLAN / Media sharing interface.  

  @Joseph-TP Sorry about my typo.  Yes, I meant DLNA, not DLAN media device.  And, thank you for the pointer to the brief discussion of Media sharing in the user guide.  This is exactly the functionality that I need more information on.

That discussion in the User Guide only provides a minimum amount of information.  Some questions that I have is how to add new music to the media device?  How to remove old music from the media device?  There does not appear to be any explanation for why the media shared device seems to be read-only.  In my case, the Music folder at the root of the file system share reflects the Music folder of the media share.

Finally, one important question is at the root of the file system share is a hidden directory called ".TPDLNA", in this is the reflection of the files that are shared in the Media share.  But, I am not sure,  I've not found any documentation for this.  Do you know of any additional sources for the Media Share on the AX55 router - such as the questions that I have raised?