Move Assignee from one doc to another when transitioning

Hello Community. I’m tripping over something and it became a mandatory for the project I’m working on.

User story: we assign a user (from the sidebar) on an Opportunity and we create “ToDo” while doing so (user with a role of “Sales User”). When the assigned user creates a Quotation for the Opportunity, there’s no way we can tell who is working on what unless we go into the document and see the document log.

So, how can we transition Opportunity’s assigned user to Quotation document automatically? Or at least pull up the user’s data such as “First and last name” to the quotation document itself?

Thanks guys, stay healthy.