Yes, I understand, but Q5 settings can only be accessed via the Fiio Music app on Android or iOS. There is no option in PC USB driver. Or at least that was the case last time when this was discussed in the Q5 thread.
I have version 4.13.0 of USB driver with fewer tabs at the top. I see now there's a newer version >>
https://www.fiio.com/Driver_Download
What version do you have installed?
So if you want to save a new balance setting that will "stick" inside the Q5 you'll have to access it via the FiiO Music app in Bluetooth mode.
But if you want to temporary tweak the balance when connected to PC in Windows you can access that setting in the properties window of the sound device: