Cannot add children to Midi device

[jln-]

Using v3.0.0-a18, once having created a Midi input device (without the 'create whole tree' option), right-click on the device name display the 'add children' option in the contextual menu. When selecting it, nothing happen.

If building Midi namespace 'by hand' is not supported, the option should be greyed out in the contextual menu.

If supported, then there is a bug. :-)