The queue functionnality seems to function well only if there is only one queue per module.
Install ECA Module and create multiple distributed queue.
Then only one queue shows up, as the ID is always the same (name of the module) even though you may have multiple queues.
Change the way the array of the $definition variable is built (not with the ID).
Queue UI functions well so maybe we can see there how it's done properly.
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Sure, happy to see something like this get in. Perhaps in Drupal\simple_cron\Plugin\SimpleCron\Queue::getTypeDefinitions() to avoid breaking change (haven't checked, but guessing there would be one), could check if the definition exists and if so append some sort of '_' . $count to it so e.g. `eca`, `eca_2`, `eca_3`...