Hi Mario,
Please check following screenshot about how to add new field on search view. If the field is not included in SAP standard, then you need to create this field by AET.
1.click Personalize on right top and then enable configuration mode under personalize settings.
2.then on the search view, you will see the configuration button(gear) on right top, click it, then
put cursor on search view and click your mouse. In open pop up, you can see if your required field
is in "available search criteria", if so, you can add it to right side "selected search criteria". If not,
then this means your required field is not in sap standard, you need to create your own by AET.
Best Regards,
Bruce