Outright has just released the ability to delete multiple transactions at once.
New users, you're probably thinking, "what a great addition!", while older users are thinking, "finally!" Whichever group you fall into, we're sorry it took so long but it's here now!
Where can you find this feature?
From the Income or Expense tabs, simply click on "Edit Multiple." Once you've selected at least one transaction, you'll see the option to delete those transactions at the bottom/right of the Edit Multiple box.