A sidebar block plugin that allows the user to navigate by articles and issues has been released in the plugin gallery for OJS 3.4 and on https://github.com/mpbraendle/navigation
You can try it out on https://www.chimia.ch - on the issue page at “Browse Issues”, on the article details page at “Browse Articles”. Here one can traverse to the previous or next article / issue without having to step up to the table of contents or archive of issues.