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.
{ "listunspent", 4, "query_options" },
    { "listunspent", 4, "minimumAmount" },
    { "listunspent", 4, "maximumAmount" },
    { "listunspent", 4, "maximumCount" },
    { "listunspent", 4, "minimumSumAmount" },
    { "listunspent", 4, "include_immature_coinbase" },
    { "getblock", 1, "verbosity" },
    { "getblock", 1, "verbose" },
    { "getblockheader", 1, "verbose" },
    { "getchaintxstats", 0, "nblocks" },
    { "gettransaction", 1, "include_watchonly" },
    { "gettransaction", 2, "verbose" },
    { "getrawtransaction", 1, "verbosity" },
    { "getrawtransaction", 1, "verbose" },
    { "createrawtransaction", 0, "inputs" },
    { "createrawtransaction", 1, "outputs" },
    { "createrawtransaction", 2, "locktime" },
    { "createrawtransaction", 3, "replaceable" },
    { "decoderawtransaction", 1, "iswitness" },
    { "signrawtransactionwithkey", 1, "privkeys" },
    { "signrawtransactionwithkey", 2, "prevtxs" },
    { "signrawtransactionwithwallet", 1, "prevtxs" },
    { "sendrawtransaction", 1, "maxfeerate" },
    { "sendrawtransaction", 2, "maxburnamount" },
    { "testmempoolaccept", 0, "rawtxs" },
    { "testmempoolaccept", 1, "maxfeerate" },
    { "submitpackage", 0, "package" },
    { "combinerawtransaction", 0, "txs" },
    { "fundrawtransaction", 1, "options" },
    { "fundrawtransaction", 1, "add_inputs"},