So I tried to unpack the mod paks with Fmodel to get some tracks and mix or edit paks to make custom soundtrack.
I see that each pak has directory in System Shock/Content/Sound/Music/CustomMusic where are placed some playable and exportable tracks, but in every pak there are only original tracks, with the exception of main menu music in some paks. So where are the new tracks which mod actually adds into game? How do I get the .ogg files for tracks used in these mods?
I wish I could say, but I used this tool:
https://www.nexusmods.com/systemshock2023/mods/78