After fixing all the problems we know due to the automated upgrade process 2.1.1 → 2.1.2 ,

asking CS CART support: if new Quicksearch functions needed to be enabled cost me 5 support credits.

If anyone interested, Quicksearch can be enabled and edited in ADMINISTRATION / ADD ONS

Details here → http://https://www.cs-cart.com/reference-guide.html

(To be fair they did not charge anything and presented excuses after fixing the upgrade mess 2.1.1 → 2.1.2)