How can we access the values on the content-manager form model?

I’m doing some logic on the relations controller, to change things depending on whats on the rest of the form. How can I access the content-type data who populates the form?

Let’s say I want to filter the relation dropdown options depending on a value that is on some other part of the form. I imagine there is already an object linking this data to the form fields. Is this object global? Can I access it from the relations controller via strapi.something?

Is my approach completely wrong? I’m new so any help is appreciated.

Thanks in advance.

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