I downloaded Sparrow, first created a new wallet, and then selected to import it into the Software Wallet. There is a Master Private Key (BIP32) inside, but I found that it can only be imported here,
Private key in xprv/zprv format
May I ask how to import a WIF format private key? Thank you!
Sparrow doesn't support single private key WIF wallet import, you can only import master private keys xprv which is a legacy address and zprv for native segwit address on sparrow wallet.
You can use the sweep wallet address on sparrow and import it on Electrum wallet, it's light and can be use as airgap wallet or run offline completely but you are going to need two device, one without internet and one with internet.
Follow this guide:
https://bitcointalk.org/index.php?topic=5524213.msg64885706#msg64885706