If I create an RBF transaction using the Qt GUI but specify my own custom change address, bumpfee doesn't work because it claims it can't find the change address:

    "Transaction does not have a change output"

This is because none of the outputs satisfy

    pWallet->IsChange(...)

I see there's a "TODO" commented in `CWallet::IsChange()` in `src/wallet/wallet.cpp`:

    // TODO: fix handling of 'change' outputs. The assumption is that any
    // payment to a script that is ours, but is not in the address book
    // is change.

I tend to put all my addresses in the address book whether I'm going to use them as change or not. I guess if the wallet was capable of creating its own SegWit change addresses I'd stop using custom change addresses, but currently it always seems to send change to a legacy address if I don't manually specify a change address.
new_coin_control.m_feerate = EstimateFeeRate(wallet, wtx, old_fee, new_coin_control);
    }
    
    
    
    
    
    
    
    for (const auto& inputs : wtx.tx->vin) {
        new_coin_control.Select(COutPoint(inputs.prevout));
    }
    new_coin_control.m_allow_other_inputs = true;
    
    new_coin_control.m_min_depth = 1;
    constexpr int RANDOM_CHANGE_POSITION = -1;
    auto res = CreateTransaction(wallet, recipients, RANDOM_CHANGE_POSITION, new_coin_control, false);
    if (!res) {
        errors.push_back(Untranslated("Unable to create transaction.") + Untranslated(" ") + util::ErrorString(res));
        return Result::WALLET_ERROR;
    }
    const auto& txr = *res;
    
    new_fee = txr.fee;
    
    mtx = CMutableTransaction(*txr.tx);
    return Result::OK;
}
bool SignTransaction(CWallet& wallet, CMutableTransaction& mtx) {