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.
{"fee_rate", RPCArg::Type::AMOUNT, RPCArg::DefaultHint{"not set, fall back to wallet fee estimation"},
                             "\nSpecify a fee rate in " + CURRENCY_ATOM + "/vB instead of relying on the built-in fee estimator.\n"
                             "Must be at least " + incremental_fee + " higher than the current transaction fee rate.\n"
                             "WARNING: before version 0.21, fee_rate was in " + CURRENCY_UNIT + "/kvB. As of 0.21, fee_rate is in " + CURRENCY_ATOM + "/vB.\n"},
                    {"replaceable", RPCArg::Type::BOOL, RPCArg::Default{true}, "Whether the new transaction should still be\n"
                             "marked bip-125 replaceable. If true, the sequence numbers in the transaction will\n"
                             "be left unchanged from the original. If false, any input sequence numbers in the\n"
                             "original transaction that were less than 0xfffffffe will be increased to 0xfffffffe\n"
                             "so the new transaction will not be explicitly bip-125 replaceable (though it may\n"
                             "still be replaceable in practice, for example if it has unconfirmed ancestors which\n"
                             "are replaceable).\n"},
                    {"estimate_mode", RPCArg::Type::STR, RPCArg::Default{"unset"}, "The fee estimate mode, must be one of (case insensitive):\n"
                             "\"" + FeeModes("\"\n\"") + "\""},
                    {"outputs", RPCArg::Type::ARR, RPCArg::Default{UniValue::VARR}, "New outputs (key-value pairs) which will replace\n"
                             "the original ones, if provided. Each address can only appear once and there can\n"
                             "only be one \"data\" object.\n",
                        OutputsDoc(),
                        RPCArgOptions{.skip_type_check = true}},
                },
                RPCArgOptions{.oneline_description="options"}},
        },
        RPCResult{
            RPCResult::Type::OBJ, "", "", Cat(
                want_psbt ?
                std::vector<RPCResult>{{RPCResult::Type::STR, "psbt", "The base64-encoded unsigned PSBT of the new transaction."}} :
                std::vector<RPCResult>{{RPCResult::Type::STR_HEX, "txid", "The id of the new transaction."}},
            {
                {RPCResult::Type::STR_AMOUNT, "origfee", "The fee of the replaced transaction."},
                {RPCResult::Type::STR_AMOUNT, "fee", "The fee of the new transaction."},
                {RPCResult::Type::ARR, "errors", "Errors encountered during processing (may be empty).",