How can I 'echo' into fd 3 to be able to use it on a gpg cmd line?

[omcujl92 at duck.com]

... (Windows 10) [DOS] cmd ... [*NOT* powershell]
... cygwin gpg ...

How can I 'echo' into fd 3 to be able to use it on a gpg cmd line?
e.g. 'echo "Secret data" | gpg.exe -c -passphrase-fd 3 3< echo %PASSWORD%'

[Ignore the need, or not, for --batch and/or --pinentry-mode loopback,
I can wrestle with those separately.]
(I am trying to avoid the passphrase from appearing in cleartext
within tasklists, etc.)


I am working on a BitWarden(-cli) backup script. So the 'echo "Secret
data"' above is actually something like:
bitwarden-cli --export json | gpg -c ... >...bitwarden_backup.json.pgp
- the hangup seems to be how to echo into 3< to be able to use it as
input, for ' -passphrase-fd 3'.

[Or 7< echo %PASSWORD%, for that matter - it seems powershell uses 3-6
for stdwarn|verbose|debug|info, and probably best to avoid potential
future conflicts.]