Problem
Is it possible to restrict access to an improvements portfolio?
Solution
Yes, you can restrict improvement portfolios to named users. First you will need to Enable the configure 'Restrict improvements module access to named users' from Admin - Improvements - Other Configurations.
Then, go to the specific Improvement portfolio - Stakeholders - Viewers - add the name of the promasters, portfolio manager, editors, approvers, assigners and closers or any other users. Now only these people will be able to view the incidents reported in that specific portfolio.