Some comments from @sipa in #12702.

___

Yes, I think `importmulti` is superior in every way, except:
* Slightly less convenient to use (it requires redundant information, as you have to explicitly state what you want to import, and then give the keys/... to enable that).
* ~Doesn't support P2SH-P2WPKH yet~. Added in #14454

The latter can be fixed by just adding support for that case. The former can be improved by adding 'default' cases (e.g. if you prove a WIF private key, it can permit omitting the address, ...).

{
    std::shared_ptr<CWallet> const wallet = GetWalletForJSONRPCRequest(request);
    CWallet* const pwallet = wallet.get();
    if (!EnsureWalletIsAvailable(pwallet, request.fHelp)) {
        return NullUniValue;
    }
    if (request.fHelp || request.params.size() != 1)
        throw std::runtime_error(
            "backupwallet \"destination\"\n"
            "\nSafely copies current wallet file to destination, which can be a directory or a path with filename.\n"
            "\nArguments:\n"
            "1. \"destination\"   (string) The destination directory or file\n"
            "\nExamples:\n"
            + HelpExampleCli("backupwallet", "\"backup.dat\"")
            + HelpExampleRpc("backupwallet", "\"backup.dat\"")
        );
    
    
    pwallet->BlockUntilSyncedToCurrentChain();
    LOCK2(cs_main, pwallet->cs_wallet);
    std::string strDest = request.params[0].get_str();
    if (!pwallet->BackupWallet(strDest)) {
        throw JSONRPCError(RPC_WALLET_ERROR, "Error: Wallet backup failed!");
    }
    return NullUniValue;
}
static UniValue keypoolrefill(const JSONRPCRequest& request)