Each channel has a "digital trim" in the mixer view for that track that can be used to set the level of the track independent of the fader. So if you use digital trim, you can set the relative levels of each track, independent of the faders. This will be saved with the song.
This is a pretty good system. Once you set the faders, if you want to save your mix, you would need to normalize with the digital trim. This may be preferable to a system that remembers scenes but has no way of setting the physical fader position. In that kind of system, you would need to physically adjust each fader when you load a song, and it could be error prone.
Of course, motorized faders are the big daddy solution, but those are not without problems and considerable cost.
The digital trim handles what you need.