\x3c and \x5c in Variables
Help advises us that if we want to use angle brackets ("<" or ">", although only "<" seems to matter) in a Variable definition, we should prefix (escape) them with a backslash ("\").
Help fails to advise us that the same is true for backslash itself, and further, that typing either "<" or "\" via their \x## hex codes can trip you up.
I wanted to create a var for the symbolic "therefore", the 3-dot triangle.
With a Character Format of Symbol defined,
I entered the definition:
<Symbol>\x5c<Default ¶ Font>
but when I hit [ Insert ], what I got was "<Default ¶ Font>" in Symbol font.
Frame had silently changed the "\x5c" to "\", ![]()
definition now: <Symbol>\<Default ¶ Font>
treated the resulting character as an escape of nothing in particular, ![]()
and then ignored it altogether. ![]()
I had to go back and revise the var def to:
<Symbol>\\<Default ¶ Font>
The same thing (symbolic <Default ¶ Font> result) happens with
"\x3c" for "<",
but not with "\x3e" for ">".
When a hex code is a printable latin character, Frame automatically converts it to that character when creating or editing a Variable definition. It neglects to advise you about this, and more egregiously, neglects to follow its own special character rules, but enforces the rules anyway.

