I have no "Public" folder

It’s Windows 10 for me, too.

@adam8281, just make a Multimedia share in the shares tab of the web UI and enable Public and media serving. It’s exactly the same as a ‘Public’ share, just with a different name.
Map the share in windows, add a Music / Video / Whatever directory.

Shares are only useful when you need advanced permissions: limit access to Pictures for yourself only, share Movies as read-only with your family, disable media serving on your business related pictures …

If you want to move the data quickly between shares, don’t use the mapped folders in windows, but use SSH (e.g. with winscp). Example moving content from /shares/Music to /shares/Multimedia/Music.
This is because moving data between mapped shares with windows will move all data through your windows machine (which is slow) while it is instant with winscp (the data doesn’t have to leave your NAS).
Note that I said moving the data (cut-paste), not copying the data… but even that goes a lot faster over SSH for the same reason.

Thanks @Tfl that’s a great suggestion