Inventory Management - set required field in MI01

I have a request to set this field "Phys. Inventory Ref." (IKPF-XBLNI) as required field in the creation of the inventory document MI01.

I went to the SPRO and was not able to find the way to add it.

Materials Management>Inventory Management and Physical Inventory>Physical Inventory>Field Selection for Physical Inventory

I only saw this one:

So, my question is, how is the way to add more fields as required?