Unicode-math: Use several calligraphic fonts in parallel

Question

I would like to use e.g. the calligraphic font from two different fonts conveniently in the same document.

For example in the snippet below, how can I load in parallel e.g. the calligraphic fonts from LatinModern and use it via a command like \symcallatin{ABC}?

I have already found some solutions that rely on switching the whole font e.g. using mathversion. But I would like to avoid this and instead have a dedicated command that allows to write certain symbols in a predefined font. How can this be achieved?

% !TeX TS-program = lualatex
\documentclass{standalone}
\usepackage{fontspec,unicode-math}

\setmathfont{TeX Gyre Pagella Math}
\setmathfont[range={cal,bfcal},StylisticSet=1]{XITS Math}

\begin{document}
    $\symcal{ABC}$ 
\end{document}

Answer 1

Combining different fonts in Math mode was traditionally implemented with the \fam primitive. unicode-math does not use \fam by default for OTF fonts, but you can change that by manually loading the fonts into mathgroups. The additional fonts are not loaded by the unicode-math machinery, so range etc. is not available:

\documentclass{article}
\usepackage{unicode-math}
\setmathfont{XITS Math}
\ExplSyntaxOn
\makeatletter
\cs_new:Npn\definemathgroup#1#2#3#4{
  \fontspec_set_family:Nnn\l_my_math_font_family{SmallCapsFont={},ItalicFont={},BoldFont={},Script=Math,#3}{#4}
  \exp_args:Nc\new@mathgroup{\string#1}
  \::c\::n\::f\:::\new@symbolfont{\string#1}{TU}{\l_my_math_font_family}{\seriesdefault}{\shapedefault}
  \cs_new:Npn#1##1{#2{\fam\use:c{\string#1}##1}}
}
\makeatother
\ExplSyntaxOff
\definemathgroup\mathmyothercal\symcal{}{Latin Modern Math}
\definemathgroup\mathtgcal\symcal{}{Tex Gyre DejaVu Math}
\begin{document}
\[ABC=\symcal{ABC}=\mathtgcal{ABC}=\mathmyothercal{ABC}\]
\end{document}

In the command \definemathgroup the second parameter(always \symcal in the examples above) select the math alphabet. This can be replaced by the other \sym... commands from unicode-math to load other math alphabets, e.g. \smybb for blackbord bold, \symfrak, \symit, \symnormal, ...