Trello – How to Control Trello List Visibility to Members

Is it possible to assign a per list visibility to certain Trello members?

I deal with contractors who I want to be able to assign tasks to but don't want them seeing all of the lists (I have "pending quotes"/"pending quote acceptance" lists) and I'd love the ability to assign visibility to a list or even better, only to tasks that a member is assigned to.

I've looked through Trello's work board and can't see any planned feature around it. I've asked members I've added if they can see all lists/tasks and they can, so by default they can see it all.

Is this currently do-able? I don't want to create separate boards, as it segments the whole workflow too much and defeats the purpose of using Trello.