For my own use, I made a few minor tweaks to Boxmarks2: Basically, for the h, i, and j characters -- the three "trilllike" ones, I tweaked it a bit so that they can overlap, making a continuous trill symbol by using, say, hiiiiiiiiiiiiiiiiiiiiii or hiiiiiij or hiiijjiiijijiji if you are so inclined, instead of one with gaps in it. Of course, they will still work fine on their own, since the change is fairly minimal.
Does anyone know who I'd ask to be able to offer it to others?
Check with Richard Woodroffe. He maintains the Scriptorium. His email address is in the Members section of this forum.