The OP was asking for an option to delete only one (or two) of the fields (CC/BCC/Reply-to) - including all their entries - with just a simple click. Simular to the previous version 1.7. which had an "X" at the end of each field.
After deleting the field (and it's entries) the user could bring back the field with the menu item "Show/Add CC/BCC"... which is now the small arrow at the end of the "To" field.
That is correct. Clicking on the arrow at the right of the To field just "hides" the filled up bcc entry. It does not delete its entry.
On most emails I do want an automatic copy sent to me. But on some I want a simple way to remove the bcc entry. The X allowed me to do that quickly and simply. I miss it.
"Show/Add CC/BCC"... then allowed me to restore the field if I changed my mind and I could re-enter what I wanted.
It would be great to have these two restored.