Then it would move each time you typed a key, if the sequence had more than two levels. That'd be bad instead of how it is now, where key in the sequence is added on the right and the tip stays where it is.
The sequence being incomplete was a bug. We've fixed that for the next beta.
I think it's too esoteric to add custom options for. Most people will never see it, and people already complain there are too many colors/fonts for them to understand.