Would it be possible now, to make a portable version of Gpg4win? They've changed the procedure, reducing it to copying files. This would allow encrypting, signing, decrypting, and verifying individual files outside of Thunderbird. For reference:
Gpg4win: Mkportable only allow portable installer with installed features
https://dev.gnupg.org/T6246
Portable version of Gpg4win
https://wiki.gnupg.org/Gpg4win/PortableVersion
Tried and after a little confusion it seems to work but I'm not familiar enough with making portable apps. One problem is this leaves the key files within the App folder rather than in the Data
folder which would probably be a problem for updates.
The latest release of Gpg4win is:
Gpg4win 4.3.1 (Released: 2024-03-11)
https://www.gpg4win.org/download.html
ADDENDUM
May leave some daemons running when exit Kleopatra:
GnuPG’s smartcard daemon (32 bit) scdaemon.exe
and
GPG-agent (32 bit) gpg-agent.exe