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In order to delete set of Scheduled Issues just select them and press the Delete Selected button:
Use the drop-down menu cloaked under the "Projects" (1) to access a desired one and then go to the below located "Scheduled Issues" (2).
"Delete Selected" (4) button becomes active when you tick (3) particular scheduled issue(s) from the list above that button.
Confirm the operation by pressing the Delete button:
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