Natively, Thunderbird doesntdoesn't support this functionality. It
It does appear to be possible with anusing a Thunderbird add-on named Attach from Clipboard
.
Herehttps://addons.mozilla.org/en-US/thunderbird/addon/attach-from-clipboard/ is ana Thunderbird add-on that may work using specific key's combination distinct standard Paste/Copy windows key's combination.