Hi
Not sure I have the same problem as I can see an MCM cat dropdown on the normal media library page, but I did have issues with galleries as the dropdown was not there.
But it was, seems like it might be a WP admin CSS thing. Use browser dev tools to find it. Also seemed to be browser width dependant if it showed up or not.
This is a real hack, and throughly not tested, but adding this to functions.php –
add_action(‘admin_head’, function () {
echo “<style>
.media-toolbar-secondary {display: flex}
</style>”;
});
made it show up.
As I say, was a very quick hack as I was on a deadline to get site up and running, but got me out of trouble !