I know the unicode of the symbols that I would like to be able to render properly in the presentation pane, but how do I type them in manually into the editor?
Universal quantifier "for every" or "for all" (upside down A)
Unicode U+2200
Existential quantifier "for each" (upside down E)
Unicode U+2203
The Windows app CharMap wasn't working for me. But I did find this app "UnicodeInput" that works great with Joplin.
UnicodeInput runs in the background. While you are in the Joplin editor, press ALT+NUMPAD-PLUS to bring up the UnicodeInput app, type in the Unicode value, hit ENTER, and it pastes in the symbol that I wanted into Joplin. HTH