I found a solution. I should have known that the authors of Koreader had thought of everything.
In my home directory,under File, Items, I checked the box entitled "Reduce font size to show more text" and experimented with "Items per page" and the font size. Koreader applies these settings to Bookmarks also. You can actually highlight about fifteen words in a document and it shows up quite legible in Bookmarks. It's beautiful!
At this point you may have to stop development, since Koreader seems perfect.