If you want the preview button to be easily accessed then I think it needs to be a sticky menu at the top. In fact, I think the whole page needs a bit of work because there is a lot of waste at the top of the admin page with that black bar that has no real use. I posted this a while back. It’s rough but it gets the point across.
https://forum.treepl.co/t/admin-ui-fixed-header/1466
Moving what’s in the current black sticky menu to the side menu would open up the top and allow for a new sticky menu based on the module. This would make things very handy as you wouldn’t have to scroll up every time you need one of these items we actually use.