Tested versions

• 4.4.1-stable
• 4.5-stable
• 4.6-dev2

System information

Windows 11

Issue description

When dragging a PackedScene into the hierarchy and adding a new material for example, all of the properties are disabled, until I both save the scene and then switch focus back and forth to the node.

I don't know if there has to be a resource stored to disk or something for these to be enabled, but then showing a yellow triangle right of node's name with a message and having it auto refresh on scene save would completely solve this confusion.

Steps to reproduce

1. Create a CSGBox3D node and save as a box_node.tscn
2. In another scene drag the box_node.tscn into it and select it
3. Under Material create new StandardMaterial3D and you'll see all of the properties disabled like in the screenshot
4. switch focus from the node and back, still disabled
5. save the scene, still greyed out disabled
6. now after saving the scene switch the focus and the fields become editable

Minimal reproduction project (MRP)

I'm not attaching a project because reproducing requires an unsaved scene.