Sequence Preset List - Any way to shorten it?

... temporarily, or to put a set of favorites at the top?

Easiest way is to make a new preset with your preferred settings, and when you name that setting, name it something that starts with a "!".

Once you've done that, spotlight search for whatever you called that setting - you'll find a file with that name. In that folder are the other sequence settings. You can delete at will.