You can create a Multi-Level Cascade Select custom field for your issues, by following this these simple steps:
Go to Settings → issues.
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Go to Custom field → click on create → Create custom field.
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Find MLCS (Advanced → Multi-Level Cascading)Cascade Select (multiple selects) in the Advanced list.
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Set a name and, optionally, a description for the new field.
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Select all screens and context where you need the contexts for the Multi-Level Cascade Select custom field.
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MLCS are now available on any issue.
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