The rename option in the anvil for the snapshot 20w10a doesn't currently work.
Related issues
duplicates
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Thank you for your report!
We're actually already tracking this issue in MC-173725, so I resolved and linked this ticket as a duplicate.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature in the future to see if the issue has already been reported.
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