On 5 Jul 2018 04:15:43 GMT, Mark Blain wrote:

For (1), your best choice really would be a GUI password manager like
KeePass (https://keepass.info). You could encrypt "password.txt"
with most any freeware compression program and open the encrypted
file with a Start- Run command to READ the passwords inside, but not
to EDIT them: for that, you'd have to extract the text first and re-
encrypt it afterward. That's not convenient or secure.

This is a much harder problem to solve, so I thank you for your astute
advice on the harder problem of efficiently accessing the users' passwd
file from the "Start Run" command interface.

I agree it's "messy" having to add the step of securely deleting the
plaintext file after the fact.

Ideally, you want to decrypt the ciphertext passwd file into memory,
visibly view or manually edit the resultant cleartext, and, when you close
down the viewing/editing window, to automatically encrypt the results and
then save only the newly encrypted results to a file, all in one fell swoop
(leaving no cleartext file except that which may remain in memory).

There are command-line encryption questions for Windows:
https://superuser.com/questions/434716/looking-for-command-line-encryption-utility-for-windows
Where not only 7zip, but also openssl, pgp/gpg, & truecrypt/viacrypt
suggestions have been offered.

None of those are native to Windows, but the cipher command looks useful:
https://www.windows-commandline.com/cipher-command-line-encryption-utility/
c:\windows\system32\cipher.exe

In that article on Windows native command-line encryption are examples:
To encrypt a file, use: cipher /A /E filename
To decrypt a file, use: cipher /D fileName

I'm sure payware solutions would work, such as this one example:
http://www.aeppro.com/products/screenshots/how-to-automate-file-encryption-from-windows-command-line.shtml
But the goal is to accomplish the task "well enough" using free methods.

I will try out some of these solutions, where they all seem to do the job!