There is no menu available for a task in a schedule when the schedule is opened read-only.
The issue is demonstrated by the following scenario:
Open a scheduler. A right-click on a task opens a context menu:
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Switch the scheduler to read-only. Now no context menu at all is opened when you right-click on it:
<Please see attached file for image>

For comparison, in V10 the context menu was also available in read-only mode:
<Please see attached file for image>
