I'm looking for a way to share a very sensitive document between Windows (read and write access) and Android (read access at least, writing appreciated but not immediately necessary). What I considered already:
Veracrypt. Works for the Windows part, but people say that the only relevant Android app (EDS Lite) has been having issues on recent versions of Android for years. Not reliable.
An encrypted archive like WinRAR has. Sadly, it has never been meant for my use case: WinRAR, for instance, decrypts and unpacks a file to be viewed to a temporary file on disk and keeps it as plaintext until WinRAR is closed. WinRAR not closed nicely, plaintext sits there forever. An absolute no go.
Encrypted PDF. Would work if not for the necessity to copy out some text from time to time. PDF is notoriously unreliable at this.
Overall, I'm at a loss and would appreciate some ideas.