Follow these steps to remove Hebcal events from Microsoft Outlook for macOS and you didn’t use the Subscription feature.
1. Open Microsoft Outlook for macOS, and uncheck all calendars except for the one that contains Hebcal events.
2. In the search box on the upper-right, type the text “hebcal” and press Return to select Events that contain “hebcal”
3. Click on the first item in the search results pane on the right. Then, Select All by using ⌘-A (Command-A) on your keyboard. Or, scroll to the bottom, and holding down the Shift key, click on the last item in the search results pane on the right.
4. When prompted Are you sure you want to permanently delete these events? click the Delete button to confirm