If you wish to link an item to a specific analytical account independently of the employee's breakdown, you must first activate this possibility in the company settings by checking the option Itemized split :
It will then be possible, in the management of the items, to assign a default account to a given item (or items):
Checking the Analytical item without specifying the default account will allow you to select it by hand in the calculation directly:
In the example above, the bonus is free. If you want it to be allocated to another account than the employee's, scroll down the list of accounts and select one.