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.
{ "sendtoaddress", 1, "amount" },
    { "sendtoaddress", 4, "subtractfeefromamount" },
    { "sendtoaddress", 5 , "replaceable" },
    { "sendtoaddress", 6 , "conf_target" },
    { "sendtoaddress", 8, "avoid_reuse" },
    { "sendtoaddress", 9, "fee_rate"},
    { "sendtoaddress", 10, "verbose"},
    { "settxfee", 0, "amount" },
    { "sethdseed", 0, "newkeypool" },
    { "getreceivedbyaddress", 1, "minconf" },
    { "getreceivedbyaddress", 2, "include_immature_coinbase" },
    { "getreceivedbylabel", 1, "minconf" },
    { "getreceivedbylabel", 2, "include_immature_coinbase" },
    { "listreceivedbyaddress", 0, "minconf" },
    { "listreceivedbyaddress", 1, "include_empty" },
    { "listreceivedbyaddress", 2, "include_watchonly" },
    { "listreceivedbyaddress", 4, "include_immature_coinbase" },
    { "listreceivedbylabel", 0, "minconf" },
    { "listreceivedbylabel", 1, "include_empty" },
    { "listreceivedbylabel", 2, "include_watchonly" },
    { "listreceivedbylabel", 3, "include_immature_coinbase" },
    { "getbalance", 1, "minconf" },
    { "getbalance", 2, "include_watchonly" },
    { "getbalance", 3, "avoid_reuse" },
    { "getblockfrompeer", 1, "peer_id" },
    { "getblockhash", 0, "height" },
    { "waitforblockheight", 0, "height" },
    { "waitforblockheight", 1, "timeout" },
    { "waitforblock", 1, "timeout" },
    { "waitfornewblock", 0, "timeout" },