If a Blackout Window is set to "Global", it is not possible to attach CIs to that Window
STEPS TO REPRODUCE
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1. In "Administration", open ServiceDesk->Changes->Change-Window
2. Create New
3. Click on TAB "2. Related CIs"
4. Toggle the "Global" checkbox
If "Global" is checked, the buttons below "2. Related CIs" become inactive
Is this by design?
CA Service Desk Manager 17.3 and 17.4
We can confirm the behavior described in the description of this case is by design. This behavior has not changed and it noted in our documentation.
Blackout Window
Indicates a schedule time period. Blackout windows are always global and cannot have CIs associated with them. This blackout can indicate a reduced support period (for example, a holiday), a corporate event, or a critical business time, such as fiscal year-end. In general, scheduled changes should only occur outside blackout windows.