Not really, in the current version. There's a preview URL — /admin/menubuilder/<group id>/vertical_sample (titled "Sprwt - Menu Builder Preview") — but it does not actually render the group ID in the URL: the template it uses always pulls whichever group is the currently active Header group, ignoring the ID you passed in. So the page is only useful for double-checking the live active header, not for previewing a footer group or an inactive group before turning it on. For a real check of a group you're about to activate, the safest option is to activate it and view the storefront in a private window, then switch back if it isn't right.