Here’s what I did, and it works: I created a property with a radio-select field. Then I created 2 main workflows and an optional Holiday workflow.
1. Create a Ticket property called ‘Business Hours?’
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1. Create 3 different workflows that kick off when a ticket is created.
SET BUSINESS HOURS
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SET NON-BUSINESS HOURS
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SET HOLIDAY WORKFLOW
Looks just like the Business Hours but sets the Business Hours to ‘Holiday’.