It should be possible to hide certain picklist values similar to Salesforce. In some cases there are standard Service Board picklist values like "Canceled" on the Appointment "Status" picklist field which cannot be hidden if part of a process. Never the less, users should not be selecting this value manually. It should be possible to hide this in the user interface and servicemax go
What is the underlying problem do you intend to solve with this idea?
Hide values users should not be able to select manually
How is the problem being addressed today, if at all?
No solution, if this causes problems then the data has to be fixed manually