WordPress only holds the hooks
information in global $wp_filter
so you can check if a hook is registered with some specified function or not. you can also use function has_filter.
But I guess you can not check that, it has been called or not on some specific execution point.
But you can do this with PHP using global variable.
Check this code
add_filter( 'get_the_excerpt', 'my_trim_excerpt' );
function my_trim_excerpt($text) {
global $filter_applied;
$filter_applied = true;
$text = wp_trim_excerpt($text);
return $text;
}
add_filter( 'the_content', 'my_content_filter' );
function my_content_filter( $content ) {
global $filter_applied;
if (isset($filter_applied) && $filter_applied === true) {
//Your code when wp_trim_excerpt is already called.
}
//my code that modifies $content
return $content;
}
Here I am using a global variable $filter_applied
and modifying value on wp_trim_excerpt
then checking it on my_content_filter