Why can I only view content published to current domain? I'm using the Administration Views modules and Domain Access. When I'm logged in as the Administrator (user 1) I can view any content across all domains at /admin/content no matter what domain I'm on.

When I'm logged in as another role (Role X), who has permission to edit any content on any domain I can only see content published to the current domain. What permission or view setting or other setting do I need to apply to allow Role X to see content published on any domain no matter what domain they're on?

The only way Role X can see everything is if I give them the "Bypass content access control" permission, which I'd rather not.
After researching the api and reading up on how the permissions work (here) it looks as if the Node Access module limits a user (who is not user 1) to only be able to see content of the domain of which they belong, regardless of their editing permissions. You could, however, play around with grants (specifically grant_edit) to try and override the active domain. I would suggest some custom script to allow Role X grant_edit, or bite the bullet and use the "Bypass content access control" permission.

I understand this probably isn't the answer you wanted, however hopefully it helps in some way!