Users roles, make a page belonging to multiple users

I have a website with a lot of users.

They are all editor (with same custom roles). They can add page and post, and edit only their own page/post.

But some users need the ability to edit some specific page/post belonging to other users (not all).

I can’t had a new role for those “special users”, because the page list they need to edit is different for each “special users”. I’ve try some plugins like co-authors-plus but the search of this plugin only find admin user when i try to add a new author to page.

Any clue on how I could accomplish that?

Add the list of allowed users as post meta data and make those data accessible for admins only.