You can use Static Blocks for the mega menu even if you use the Elementor. Just go to Elementor settings and enable it for the static blocks, not just for pages.
1) Choose “Only show children of the current category” in the Product category widget settings http://prntscr.com/ulrhv4 ?
2) Only in the page settings http://prntscr.com/ulrjjp we don’t have the global option for all the pages.
3) Go to Appearance > Widgets > add the Product categories widget to the shop sidebar and change the widget title.
4) Go to Theme options > Header builder > Sticky header > choose the fixed instead of the Smart type.
