question about aws s3 restore from glacier I think you might be using an old, unsupported version of Explorer. The old "Glacier Smart Restore" has been replaced with a newer "Glacier Retrieval Policies" under the Tools menu and "Glacier Retrieval Options" in Options.
In either case, you should be able to cancel the operation if it's in-progress. However, I cannot say for certain exactly when AWS will cancel at their end using the older version.
In the newer versions, you can monitor progress in the Queue in the UI. You can cancel the queue and start the retrieval from scratch if you want. Retrieval options (Expedited/Standard/Bulk) can't be set up granularly and changed on the fly. You can choose an option, restore the files needed and then switch to a different retrieval type for the next restore if needed.
https://www.msp360.com/resources/blog/explorer-5-0-glacier-retrieval-options/
Can you describe more about how you are you using S3 Glacier and what issues are you having? Are you moving old data from regular S3 to S3 Glacier using a lifecycle policy? Are you backing up directly to S3 Glacier for archival purposes? Or, are you trying to use Glacier for more general purpose cloud storage? Something else?