Ability to remove an Idea from a portal when more than one portal is active

Currently I have a workspace with two portals. When an idea is created and made visible to "Employees" it will show in both. One portal is meant for Customers and Employees (using the visibility settings), while the second portal is a subset of employees.

I cant make it visible to a specific portal.

I dont really want to create a separate workspace as the ides are part of that product line and once i got the stakholder input, i might want also expose the idea to the other portal.