Shoppdeveloper.com

By default the Shopp breadcrumb will display “the path you followed to get here”. And frankly, that is 
what breadcrumbs are meant to do. However this means when someone enters one of your product pages using 
a direct link, the breadcrumb will be empty. It will just show the link back to the main Shopp page. 
With this plugin installed you can use breadcrumbs that show “where you are” in the hierarchical 
structure of categories.

Shopp Default Breadcrumb Extender

Add hierachical breadcrumb to your Shopp webshop product pages.

mhopps

The plugin adds navigation links on a signle post to the previous or next post within the current category

WP Single Post Navigation Within Category

The plugin adds navigation links on a signle post to the previous or next post within the current category

Shopp Default Breadcrumb Extender vs WP Single Post Navigation Within Category