I have a desktop megamenu with alias menu-top & I have created megamenu for mobile with alias menu-top-mobile but it's not reflecting. How do I do that?
Are you using any theme? If you're, then there might be an option to configure it for mobile screens. I've to look at how you've structured your theme for the Magento store.
On the other side, if you want to use you can go for Ultimo, Porto and SM Market they do provide responsive layout and mega-menu feature.
I hope that will work for you.