How to create Playlists for my NAS (QNAP)

Hi all

Since having my NAS I try to create Playlists (m3u) to play some music on my receiver. However, I did not find the correct way to do it.
This is my hardware config:
1x NAS from QNAP with movies, MP3s and FLACs
1x Yamaha Receiver (Yamaha RX-A2020) for streaming music
1x PC (Windows 10 Pro) for creating the Playlists on my NAS

I think the problem is based on the file structure on my NAS. Is there any good tool to use for it? I will not capitulate on modern software. :)
And last but not least. Is there a way to create some playlists for FLACss too? But this is just a secondary issue.

Best Regards from Leipzig (Germany),
Marcus.