Changing the data-dept of one 'ul li' on tpl file

[qcoupat]

Hello, 

I would like to change on the source file of a module the data-depth of one li a tag. 

On the back office I added 5 different categories, which results in 5 different li a tag all with the data-depth"0". I would like to change only the first li a in order for him to have a data-depth of "1" and therefore a different css class. 

Would anyone have any recommendation or tips on how to achieve this (changing only the first data-depth to "1" and leave the others at "0"? Do not hesitate to come back to me if my message is not clear. 

Many thanks,

Prestashop: 1.7.6.7