@saunders I solved this by making registered users members for exclusive content of a collection.

I have a six or more collections but don't use the communities notion that you mention. Do you mean groups?
EDIT Ah! you mean Community as in the item/post visibility

Under Settings > User perms you can choose which users have access to which collections. However this is done per collection so only once you are in a collection can you select who can use that collection. And under group permissions there are options.

Basically select the collection > Settings > General and then select the members only option and follow that with the use rand group options to fine tune what collection each user can interact with, view, post etc.

@amoun thanks for your advice. It is not my intention to limit the access to a collection to community. The collection should remain public. But there should be single posts in this collection, which are only visible for community (and here exclusively for the community of this collection). For paying users (members) there should other posts be visible, only for them.
I.e. it is about a hierarchical visibility of posts for public, community and members and limited to one collection.

@saunders wrote earlier:

@amoun thanks for your advice. It is not my intention to limit the access to a collection to community. The collection should remain public. But there should be single posts in this collection, which are only visible for community (and here exclusively for the community of this collection). For paying users (members) there should other posts be visible, only for them.
I.e. it is about a hierarchical visibility of posts for public, community and members and limited to one collection.

Still having a problem with what you want :(

The collection should remain public. But there should be single posts in this collection, which are only visible for community
That can, and only be done, by individual post

Here is a summary of possible statuses:
Public: Visible by anyone
Community: Visible by logged-in users only
Members: Visible by members only
Review: Waiting for moderator review
Private: Visible only by:
the owner/author of the post/comment,
the owner of the collection (through the main category of the post)
and collection administrators;

1. So the default is Public
2. Community is for logged in users
3. members can be for paying users

You could even use the Private option and make very special users administrators and then remove privileges you don't want admin to have would like, but then you can create your own groups with specific access

I hope I am not muddying the pond here ??

Community visibility means any logged in user will see it.
Members visibility allows you to restrict to a specific set of users.
If you need 2 sets of restricted content, then you need 2 collections.
You might be able to glue the 2 collections together with an aggregated collection but I am not sure the permissions will be checked the same way in this case.