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.
{
public:
    std::string methodName; 
    int paramIdx;           
    std::string paramName;  
};
/**
 * Specify a (method, idx, name) here if the argument is a non-string RPC
 * argument and needs to be converted from JSON.
 *
 * @note Parameter indexes start from 0.
 */
static const CRPCConvertParam vRPCConvertParams[] =
{
    { "setmocktime", 0, "timestamp" },
    { "mockscheduler", 0, "delta_time" },
    { "utxoupdatepsbt", 1, "descriptors" },
    { "generatetoaddress", 0, "nblocks" },
    { "generatetoaddress", 2, "maxtries" },
    { "generatetodescriptor", 0, "num_blocks" },
    { "generatetodescriptor", 2, "maxtries" },
    { "generateblock", 1, "transactions" },
    { "generateblock", 2, "submit" },
    { "getnetworkhashps", 0, "nblocks" },
    { "getnetworkhashps", 1, "height" },