You are right that we "could" do something there similar to how we handle it in page settings. I've logged a request in our project tracker for future consideration. For now I recommend just use content manager to move an instance. Note that for most features it is a bad idea to be moving an instance around from page to page, its ok for Html content but not for things that use friendly urls like Blog, WebStore etc. Once those features have been placed on a page and content has been created it is a bad idea to move them to another page because the friendly urls have the original page id in the real url mapping. So moving content around from page to page should be a not very common thing to do in general.