I have done my obligatory web search on the topic but came up with nothing.
I can't find any mention of a way to adjust the left/right audio balance, and I do not recall anything even MAFW Equalizer having that option.

I don't have time right now to test the effects, but if its even possible,
alsamixer in the console and the keys q/z e/c should help you.

I tried it with chroot-ed kali with alsamixer and it works just fine; Q and E is for increase left and right "channel", Z and C is for decrease.

ok, thanks...
Works great, kind of, but if the terminal is even minimized to do anything else not to mention closed the setting change dies. You have to go back and nudge the settings up or down to refresh them.
Now for me it is a fix for I think sloppy solder shorting a SM resistor in a BT headset, but it is a PITA when I also need to do stuff beyond music or audio books that I can't control exclusively with the answer,pause fwd,bkwd buttons on the BT dongle.
edit:
Alsamixer also times out after something like 30-60min.

Thank you for that observation, biketool. I was going to embarrass myself by asking if the settings are permanent (as in, to they survive a reboot). You cleared that up for me

Quite frankly, I would find a solution with a limitation like that quite useless. I am lucky that I do not need it. Yet.

Well damn.
I messed up above and had my ground and left channel soldered in reversed the BH-214 so of course left was messed up, I am surprised with the performance of the right actually. Once I soldered to the correct pads all is working correctly that I don't need the alsamixer, but still a cool hack. I just had to look and see the sleeve in the trs jack went to the pad in the ground layer of the PCB. oops...