All category, payee and tag-based reports can be generated for "Transfers" option as well. You'll find that option next to listed categories, payees or tags, respectively.
There are few important things to note:
transfer will not appear in the report if both "From" and "To" accounts are included in the report,
if you generate an income-based report, you'll only see the incoming parts of the transfer (coming from accounts not included in the report). Vice-versa for expense-based reports,
that being said, even if both accounts are included in the report but those accounts are in different currencies (and so the transfer is multi-currency), then MoneyWiz will calculate gain/loss from currency exchanges and also list this under the "Transfers" label,
since transfers to loan accounts have category assignments of expense categories, both sides of this type of transfer will be included in the expense category report only.