Hi Jose,
If you have the Close Button of the Off canvas menu to appear Inside in Appearance > Customize > Layout > Off Canvas Panel, you may add a PHP snippet like this to alter it:
add_filter( 'generate_close_slideout_navigation_button', function() {
return sprintf(
'<button class="slideout-exit %2$s">%1$s</button>',
'YOUR CUSTOM HTML HERE',
'has-svg-icon'
);
} );
Kindly replace YOUR CUSTOM HTML HERE
with your HTML.
Adding PHP: https://docs.generatepress.com/article/adding-php/#code-snippets
Adding it through Code Snippets should work.
Hope this clarifies. Kindly let us know how it goes. 🙂