Quick answer: Godot 4 C# [Export] of Godot.Collections.Array<Resource> not showing typed Resource pickers? Generic type erased at marshalling - use Godot.Collections.Array<MyResource> with concrete type.
Inventory holds Array<Resource>. Inspector shows generic Object pickers, not Item pickers.
Use concrete type
[Export] public Godot.Collections.Array<Item> Items {{ get; set; }}Concrete typed array; inspector shows Item pickers.
Or PropertyHint
[Export(PropertyHint.ArrayType, "Item")] with element class. Works for older Godot versions; verbose.
Verify in inspector
Drag-drop should only accept Item assets. Generic Object accept = the typing is lost.
“Typed collections in C# need explicit type parameters. Godot's marshaller doesn't infer.”
Audit your Resource collections for explicit typing. The inspector UX is the visible signal.