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.
{"includeWatching", UniValueType(UniValue::VBOOL)},
                {"include_watching", UniValueType(UniValue::VBOOL)},
                {"inputs", UniValueType(UniValue::VARR)},
                {"lockUnspents", UniValueType(UniValue::VBOOL)},
                {"lock_unspents", UniValueType(UniValue::VBOOL)},
                {"locktime", UniValueType(UniValue::VNUM)},
                {"fee_rate", UniValueType()}, 
                {"feeRate", UniValueType()}, 
                {"psbt", UniValueType(UniValue::VBOOL)},
                {"solving_data", UniValueType(UniValue::VOBJ)},
                {"subtractFeeFromOutputs", UniValueType(UniValue::VARR)},
                {"subtract_fee_from_outputs", UniValueType(UniValue::VARR)},
                {"replaceable", UniValueType(UniValue::VBOOL)},
                {"conf_target", UniValueType(UniValue::VNUM)},
                {"estimate_mode", UniValueType(UniValue::VSTR)},
                {"minconf", UniValueType(UniValue::VNUM)},
                {"maxconf", UniValueType(UniValue::VNUM)},
                {"input_weights", UniValueType(UniValue::VARR)},
            },
            true, true);
        if (options.exists("add_inputs")) {
            coinControl.m_allow_other_inputs = options["add_inputs"].get_bool();
        }
        if (options.exists("changeAddress") || options.exists("change_address")) {
            const std::string change_address_str = (options.exists("change_address") ? options["change_address"] : options["changeAddress"]).get_str();
            CTxDestination dest = DecodeDestination(change_address_str);
            if (!IsValidDestination(dest)) {
                throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Change address must be a valid bitcoin address");
            }
            coinControl.destChange = dest;