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.
{ "fundrawtransaction", 1, "include_unsafe"},
    { "fundrawtransaction", 1, "minconf"},
    { "fundrawtransaction", 1, "maxconf"},
    { "fundrawtransaction", 1, "changePosition"},
    { "fundrawtransaction", 1, "includeWatching"},
    { "fundrawtransaction", 1, "lockUnspents"},
    { "fundrawtransaction", 1, "fee_rate"},
    { "fundrawtransaction", 1, "feeRate"},
    { "fundrawtransaction", 1, "subtractFeeFromOutputs"},
    { "fundrawtransaction", 1, "input_weights"},
    { "fundrawtransaction", 1, "conf_target"},
    { "fundrawtransaction", 1, "replaceable"},
    { "fundrawtransaction", 1, "solving_data"},
    { "fundrawtransaction", 2, "iswitness" },
    { "walletcreatefundedpsbt", 0, "inputs" },
    { "walletcreatefundedpsbt", 1, "outputs" },
    { "walletcreatefundedpsbt", 2, "locktime" },
    { "walletcreatefundedpsbt", 3, "options" },
    { "walletcreatefundedpsbt", 3, "add_inputs"},
    { "walletcreatefundedpsbt", 3, "include_unsafe"},
    { "walletcreatefundedpsbt", 3, "minconf"},
    { "walletcreatefundedpsbt", 3, "maxconf"},
    { "walletcreatefundedpsbt", 3, "changePosition"},
    { "walletcreatefundedpsbt", 3, "includeWatching"},
    { "walletcreatefundedpsbt", 3, "lockUnspents"},
    { "walletcreatefundedpsbt", 3, "fee_rate"},
    { "walletcreatefundedpsbt", 3, "feeRate"},
    { "walletcreatefundedpsbt", 3, "subtractFeeFromOutputs"},
    { "walletcreatefundedpsbt", 3, "conf_target"},
    { "walletcreatefundedpsbt", 3, "replaceable"},