Paul you could bind Magnus to a key and have it open via that. Or better yet since 19.10 doesn't have any trace of Compiz in it, use the 0.9 branch by installing compiz from Ubuntu's repos or follow my instructions here for a comprehensive of installing the old branch maintained by Scott Moreau.
Either way, you can select Compiz from mate-tweak once installed, or if you are uncertain of its stability add in an autostart command to execute compiz --replace and if things get a bit pear-shaped you can delete the autostart entry from $USER/home/.config/autostart
to use once more the preference defined via mate-tweak.
$USER/homecan also be called with$HOME, or~. For some commands, using shorthand respected by your shell inx-terminal-emulatorelsewhere may not work as expected.