I was, a year back, reassigned from one job role where I had a manager who was assigning me plenty of work, to a new project role with a different manager, who generally isn't assigning me any work. This is in a project where there is a lot of work and system improvements that can be done.
What I've tried
I've attempted to discuss the matter with the manager on numerous occasions, both via email and in personal. Emails are ignored, and they will actively make themselves busy talking to other people to block any attempts at face to face engagements.
When I do finally get a face to face engagement, I get what can only be described as vague excuses (such as 'there's no work appropriate for you!' - this is despite having an equal competency to other team members who will consult me for advice).
Normally, if a manager can't find work for me, I will do my best to engage in other work or tasks.
I can't generally do documentation as I'm largely kept out of other processes, and thus don't understand them. What I can document, I've already documented.
Anything I build to streamline or improve the system requires approval from the manager, which he never gives. Any suggestions or proposals for improvement I make typically get assigned to someone else to perform.
Assisting other team members
If I ask other team members if they have sub-tasks for me, they will happily give any they have to hand, which is usually not that many, but often I complete these in quick order and they're quite minor. In reality, I shouldn't have to fish for work from other team members, I should be assigned those from my manager.
Assisting other departments
If I try to pull non-priority tasks from other departments (who are happy for me to stop working on them at any time), the manager explicitly forbids me from working on tasks from other departments.
I can't work on any of the project, I can't document, I can't assist other departments, and I can only help team members - who are arguably equals - in small ways, I can't convince the manager to assign work. It almost reeks of constructive dismissal to me (or at least an attempt to drive my presence away from the team in the hopes I get reassigned back). There have been no complaints about my prior work and no specific issues raised.
Bearing in mind the manager has avoided as much paper trail as possible (by ignoring emails and basically forcing in-person discussions), how should I go about tackling this situation?
(I'd prefer not to quit as I liked the previous manager and I don't really want to let this manager 'win'.)