Thank you for your comments.
I have found it, but is it possible to develop and customize everything you need with the studio module or are there limits to development with this module?
I also want to know if these specific developments are still there and not lost even if an update is made.
Thank you again.

You can define and manage new custom fields but you will not be able to modify core Odoo fields using Studio. For changes to core Odoo fields you will require a code based customization.

The custom fields defined through Studio will not be lost when you do an update.

Studio is a great tool but it does not cover all of the customization scenarios. Only a code based customization covers all of the customization scenarios.

Hope this helps.

Hello,
I managed to find and add a calculated field.
Now I need to add a calculation field that calculates the sum of the amounts of the non-taxable rows and another field that calculates the sum of the amounts of the taxable rows. Is there a way to do this? and how can I access the value of the amount of each row?
Thank you for your help.