How to make a field mandatory in a maintenance work order operation?

Hi everyone, maybe you can help us…

We need the "work to be acomplished code" field to be required in the maintenance module's work order operations. We've tried both the sandbox and the Popup Customizations Using Page Composer, but we can't find the field.

So, how can we make the "work to be acomplished code" field mandatory on a work order in the maintenance module?

Thank you in advance!