Confirming that this is still an issue in Xcode 13.0 beta 3.

I made just a couple of changes to the plist to get your sample to work: For the plist, my new fragment looks like this: <key>UTExportedTypeDeclarations</key> <array> <dict> <key>UTTypeConformsTo</key> <array> <string>public.data</string> </array> <key>UTTypeIdentifier</key> <string>com.devian.sampleapp.customstring.dragdroptype</string> </dict> </array> And that's it, your code unmodified works now.

Xcode 12.5 beta 3 seems to have resolved this issue.

Any chance of this ("there's a bug in the seed that prevents sharing state between windows and the main menu") being resolved? As of macOS 11.1 beta 2, this still doesn't work.

Did you resolve this? I have same question.

Did you resolve this? I have same issue.