Removing top parent from breadcrumbs

You can write a hook into the bcn_after_fill action and remove the breadcrumb (see https://mtekk.us/archives/guides/conditionally-remove-home/ for an example for the home breadcrumb). If you don’t want to write any code, there is an extension (Breadcrumb NavXT uManager) which allows you to disallow a term/post from showing up in the breadcrumb trail.

However, if you are just doing this to keep the trail to a reasonable length, you can use CSS to shorten the individual breadcrumbs (see https://mtekk.us/archives/guides/trimming-breadcrumb-title-lengths-with-css/).