Wie erzeuge ich hochgestelltes Zeichen (Superscript) in Menü und Seitentitel?

if you are having this a lot and only on copyright, tradmark etc. you can do this in one short snippet for child-theme functions.php:
just place that character and let the script do the sup-wrapper

function wrap_copyright_text_with_sup(){
?>
<script>
(function($) {
$(document).ready(function() {       
     $('body :not(script)').contents().filter(function() {
        return this.nodeType === 3;
        }).replaceWith(function() {
            return this.nodeValue.replace(/[™®©]/g, '<sup>$&</sup>');
     });
});
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'wrap_copyright_text_with_sup');

if you like to have manual control just place vor Menu Items in Navigation Label : <sup>ABC</sup>
or to have it sub similar to it H<sub>2</sub>O
edit menu-item ( red circle ):

Well you had to use these characters: ™ ® © then the code will do the rest. A TM will not work.
It works on my end here.
Even in breadcrumb – they will be replaced. But if you like to have it

But if you even want to have it on:

then you had to copy&paste the character on f.e.: http://unicode.e-workers.de/entities.php
or use the unicode decimal for it e.g: ® in the page title
sorry boardsoft will immedeitately transfer the entity :

but in this case i would like to inspect your live page to see what is causing it.
if you could not post your page link here – send me an e-mail – or wait till mods are here.
on my testpage this is not the way you described it. see H2O and ® in the menu. https://webers-testseite.de/