The new `getrpcinfo` shows a list of the active commands and the duration each command has been running. This sounds like a good place to report a completion percentage for any command doing a blockchain rescan, to solve [this problem](https://bitcoin.stackexchange.com/q/83236/90721).
bool reserve()
    {
        assert(!m_could_reserve);
        std::lock_guard<std::mutex> lock(m_wallet->mutexScanning);
        if (m_wallet->fScanningWallet) {
            return false;
        }
        m_wallet->m_scanning_start = GetTimeMillis();
        m_wallet->m_scanning_progress = 0;
        m_wallet->fScanningWallet = true;
        m_could_reserve = true;
        return true;
    }
    bool isReserved() const
    {
        return (m_could_reserve && m_wallet->fScanningWallet);
    }
    ~WalletRescanReserver()
    {
        std::lock_guard<std::mutex> lock(m_wallet->mutexScanning);
        if (m_could_reserve) {
            m_wallet->fScanningWallet = false;
        }
    }
};
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, bool use_max_sig = false) EXCLUSIVE_LOCKS_REQUIRED(wallet->cs_wallet);
int64_t CalculateMaximumSignedTxSize(const CTransaction &tx, const CWallet *wallet, const std::vector<CTxOut>& txouts, bool use_max_sig = false);
#endif