Welcome back to the forum, @darren. I am sorry no one has replied to you over the last 2 days.
In my own case, I found Blocs’ Navigation too limiting, which led me to create my own navigation from the ground up. You can read through my journey in the following 4 threads (one thread even provided an example document in Blocs 3 format you can test):
Here’s an example page from one of my Blocs-made websites that show my megamenu:
If you shrink the width in the browser, you can see the burger menu. I basically had to create two different menus, one for LG and the other for mobile. I used visibility and code to hide and show them. It took me a long time to figure out because no one had done that before in Blocs. And I don’t know a lot of folks who do it the way I did because they seem content with Blocs’ built-in functionality. But as your site grows, a megamenu becomes more important, which is why I wanted one.