In the CRM Ribbon Workbench, how can I hide the Closed as Won button on the Opportunity form based on field in a related entity?

In the Ribbon Workbench, how can I hide the "Closed as Won" button on the Opportunity form based on a text field (accountnumber) in the Account entity? Issue description How can I hide the "Closed as Won" button on the Opportunity form based on a text field (accountnumber) in the Account entity? Each Opportunity can have one associated Account. If the accountnumber field is blank, I want the button to be hidden. I'm assuming I should use a Value Rule, but I don't know exactly how to do this for related entities. If this is not possible to do, what would be the best workaround?

I also have a 2nd related issue. I want to be able to hide the "Collaborate" button that is used for Teams integration, but can't seem to do that in the ribbon workbench either.

You have many solutions... just two of them:

1. Write a custom javascript that retrieves the value of the related account using web api (here some examples: https://butenko.pro/2018/11/13/showing-ribbon-button-based-on-the-result-of-async-operation/)
2. Add a text calculated field on the opportunity pointing to the accountnumber of the related account (the syntax for the calculated field is "[lookup name of the account].accountnumber". Then you can use a ValueRule on the new field