Thank you for your reply, Alessandro. A few of the features on my mind stem from quirks of Winboard that slowly erode my patience.
First is the excessively cumbersome edit position mode. I come across a middlegame position somewhere that I want to set up and think to myself, "Aw, geez, not again." I have a few ideas in my mind of how it should be, but I digress...
Second is the minor annoyance of pasting a game fragment and not being directly in edit game mode, having to manually switch to it to fool around with the position.
Third is the typing in of moves. I favor keyboard input for most things and find myself typing in moves most of the time. The thing that annoyed me with that at first was how I had to capitalize for Bishop in order to disambiguate when it was completely unnecessary. That got me thinking about how cumbersome the whole process was, such as having to press enter every time. I thought that there should be some "smart typing" capability similar to "smart move" entry. I.e., minimalize typing input by making the move as soon as the input is unambiguous. For example, only typing one "o" for castles, or "6" for Bh6 when that is the only piece that can go to the sixth rank. Of course, this whole smart typing concept is superfluous, and I'd be happy with just the bishop disambiguation.
Fourth is an extension of edit game mode that is similar to Scid's trial mode. For example, I paste a game and start playing through it. I get to move 20 and wonder what would happen after Black plays such-and-such. I hit "t" for trial (or whatever), play a few moves, hit "t" again to zoom back to where I left off on the main game and continue along my merry way. Normally if I made a different move, the whole game would be supplanted by that one move.
Lastly, window controls (minimize, close) on board sizes smaller than "slim."
That's all I can think of for now. If anything else comes to me, I'll be sure to holler.
P.S. Good luck on your current brainchild.