This would allow wallet operations like funding transactions with smart contract-based inputs such as LN, or any input the Core wallet doesn't know how to sign for.

https://github.com/bitcoin/bitcoin/pull/17211#issuecomment-933674310
bool IsSpent(const uint256& hash, unsigned int n) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    bool IsSpentKey(const uint256& hash, unsigned int n) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    void SetSpentKeyState(WalletBatch& batch, const uint256& hash, unsigned int n, bool used, std::set<CTxDestination>& tx_destinations) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    bool DisplayAddress(const CTxDestination& dest) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    bool IsLockedCoin(uint256 hash, unsigned int n) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    bool LockCoin(const COutPoint& output, WalletBatch* batch = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    bool UnlockCoin(const COutPoint& output, WalletBatch* batch = nullptr) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    bool UnlockAllCoins() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    void ListLockedCoins(std::vector<COutPoint>& vOutpts) const EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    /*
     * Rescan abort properties
     */
    void AbortRescan() { fAbortRescan = true; }
    bool IsAbortingRescan() const { return fAbortRescan; }
    bool IsScanning() const { return fScanningWallet; }
    int64_t ScanningDuration() const { return fScanningWallet ? GetTimeMillis() - m_scanning_start : 0; }
    double ScanningProgress() const { return fScanningWallet ? (double) m_scanning_progress : 0; }
    
    void UpgradeKeyMetadata() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    void UpgradeDescriptorCache() EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    bool LoadMinVersion(int nVersion) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet) { AssertLockHeld(cs_wallet); nWalletVersion = nVersion; return true; }
    
    void LoadDestData(const CTxDestination& dest, const std::string& key, const std::string& value) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
    
    int64_t nRelockTime GUARDED_BY(cs_wallet){0};