This is not a support issue, but rather, an external edit usage hint. I'll share my "Aha!" moment (may be obvious to others).
I had been frustrated by inconsistency with changes externally edited not being picked up (noticed) in Joplin. Joplin would sometimes see changes saved by the external edit and sometimes not, even within the same external edit session. In my case, the editor is "Epsilon", an EMACS-style programmer's text editor.
Observing Joplin behavior in log.txt, I came to the revelation that my editor's save operation of creating a .bak backup file when saving the edited file might be preventing Joplin's ExternalEditWatcher from seeing the target file change.
Ever since getting in the habit of disabling want-backups for the .md file's edit session so that saving always rewrites the target file, whenever I save, Joplin has reliably picked up my changes. Halle-freakin'-lujah!