There is no way to remove a specific queued SnackBar once it’s been enqueued but not yet displayed (or after it has already dismissed itself). Calling .close() only works on the currently visible SnackBar; attempts to close one further back in the queue throw:

dart
final sb1 = ScaffoldMessenger.of(context).showSnackBar(...);
final sb2 = ScaffoldMessenger.of(context).showSnackBar(...);
final sb3 = ScaffoldMessenger.of(context).showSnackBar(...);
sb2.close(); // throws because sb2 is not the active SnackBar

Technical Impact:

• Uncaught exceptions when trying to close a non-active snack bar.
• Poor UX: Unable to cancel outdated or no-longer-relevant messages before they appear.
• Workarounds required (try/catch, flush entire queue) that are clumsy and break user expectations.
• Inconsistent API: removeCurrentSnackBar exists for the active item, but nothing for arbitrary queued items.

Fixes #168211

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I signed the CLA.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• I followed the breaking change policy and added Data Driven Fixes where supported.
• All existing and new tests are passing.

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