Is there an "undo" ability available?

I accidentally deleted the wrong item - is there any way to undo a deletion?

You can check it in the Trash menu item on the left.
Items deleted with the Delete button or Ctrl+Shift+Backspace hotkey are moved to trash.

I clicked and selected Delete from the drop-down. It looks like it did go to the trash.

But is there an undo option in general?

No, undo is not yet implemented.