Hi Stefano,
We regret for the inconvenience caused.
Currently, we do not provide support for Enabling or Disabling a single item, now we can only disable/Enable the Listbox control.
We have created a new incident for this query. And the incident link is given below:
www.syncfusion.com/support/directtrac/incidents/135263
Please follow up in the above incident for further assistance.
Please let us know if you have any other concerns.
Regards,
Rajaveni