When updating from any version of Daedalus BEFORE version 0.12.0 (upgrading from version 0.12.0 does not cause this issue) the wallet name is removed from the wallet and replaced with <Migrated Wallet>.
Note that this issue also is related to Cardano 1.5 + Daedalus 0.13.0へのアップデートで送金時のパスワードが削除される
We have changed how data is stored and managed on the user’s machine. We retained both versions of the code for one version. But in the subsequent version, we got rid of the old code because it would be very hard to maintain both. For that reason, users who were not skipping versions retained all of the metadata (i.e wallet name). Users who skipped this version which supports both data layers lost metadata.
Please refer to the support portal article ウォレット名の変更