Issue: Cannot Share Agent to New Editor in Copilot Studio New Experience

In the current new experience, when you share an agent you can grant view/use access pretty easily, but the Editor role (which allows collaborators to edit, configure, share, and publish the agent) isn't always surfaced in the same way as the classic experience. The root cause is that sharing for collaborative authoring has a hard dependency: the target user must have the Environment Maker Dataverse security role assigned. Without it, the editor option either doesn't appear or fails silently. 

What you can do right now:

1. Use the "Classic Sharing" fallback. In the Share panel, look for the three-dot menu (…) and select Use Classic Sharing. This brings back the familiar experience where you can explicitly assign Editor rights.
2. Ensure the right Dataverse role is in place. The person you want to grant Editor access to needs the Environment Maker role in the Power Platform environment. If you're not an admin yourself, ask your system administrator to assign it. As an alternative, the System Administrator or System Customizer roles also work. 

On the roadmap question, Microsoft hasn't published a specific release date for surfacing Editor rights natively in the new UX sharing panel.