I charged 4S LiPo by mistake with LiHv settings, now my charger complains on bad chemistry. Is there a solution for this ?

I doubt a single LiHV charge with damaged severely a normal LIPO.

Just set it as a LiHV battery on your charger and discharge it down to storage voltage.

What charger do you have?

ISDT D2 MarkII, tried to storage with LiHv settings, but it says 'abnormal cell voltage'

Just stick it on your quad with the props off, arm the quad and then run the motors until the LiPo is down to 4.2V or lower. Then try balance charging / storage charging it again as a normal LiPo.

I managed to 'storage' without balance (more than once attempt), then 'charged' with balance

I think I told you to "discharge it down to storage voltage" as I assumed most chargers have the discharge function.

Discharge function doesn't care much about the voltages etc and just discharges the cells down to a specified voltage (even down to 0V if you want to dispose off the battery).

But glad you got it sorted and hopefully not much damage has been done.