Comment 69 for bug 885525

FYI.
"Archive button for delete mail", "Mark as Junk button for delete mail" is not good workaround, because bad side effect occurs and it's pretty confusing.
Another simple solution for power users/who understand Gmail/Gmail IMAP well.
- Any user can add toolbar button by "Custom Buttons" addon.
  And, such job is pretty easy for users who requested solution for this bug.
- Button script for "copy/move selected messaages to a mail folder" is pretty simple.
    Simply request "copy/move selected messaages at Thread pane to a mail folder".
- Create a button for "ordinal delete" == move to a Gmail Label which you want
  Create a button for "permanent delete" == copy to [Gmail]/<Localized trash at Gmail>"
  Because of your private script, hard-coded folder name is sufficient.
- GetSelectedMsgs() : returns currently selected messages at Thread pane.
  SharedScript(msgDBHdrs,TargetFolder,MoveMode) :
      copy mails to requested folder, if MoveMode~=true, delete msgDBHdrs.
  For "ordinal delete" : SharedScript(GetSelectedMsgs(),<Gmail Label you want>,true)
  For "permanet delete" : SharedScript(GetSelectedMsgs(),[Gmail]/<Localized trash at Gmail>)
- If required, create EmptyGmailTrash button when IMAP trash model != move to trash.
  because "Empty Trash" is greyed out if IMAP trash model != move to trash,
  "Select All + Shift+Delete at [Gmail]/Trash" is sufficient though.