3.2, eek! Earlier in development we did show existing assignments within the Homework block; however we track which user created homework assignments (for the reporting side of things among other reasons), and it appeared the only way to find out the creating user of existing assignments within Moodle was to trawl through the log tables - which gave serious performance issues as the correct indexes aren't there. We could add a feature to import existing assignments into the block if people considered it useful...?