The most useful code day-to-day is *#*#3646633#*#* to navigate to Hardware Testing -> Audio -> Normal Mode -> Type: Media . You can increase the maximum "Level 6" setting from 160 to 180 or 200 to significantly boost the headphone jack volume on your Note 11.
Before using secret codes on your INFINIX Note 11, keep the following precautions in mind: How to Use Secret Codes on INFINIX Note 11