Hybrid (open & private) assemblies and processes

Is your feature request related to a problem? Please describe.
We use the assembly module for associations that are active in our city. They are organized in groups that need to communicate "internally" as well as externally. When using Decidim, we need to open two assemblies for each (one “normal”, one with settings “private”), in order for them to be able to share private as well as public information.

Describe the solution you'd like
I think of a hybrid. The assembly should be visible and the admin able to choose for each component if it should be displayed for everyone or the closed user group.

Describe alternatives you've considered
Opening two assemblies for each organisation – very confusing for the users.

Additional context
The same is applicable with the processes.

Does this issue could impact on users private data?
no

Funded by
I put it here because our funding is already used.