It seems MDE updated overnight. You can now search for FPP not only by morning / afternoon / night, but by hour as well.
How you modify a FastPass has also changed. You can now select, “change” near the attraction to switch attractions or select “change” next to your arrival time to change the time. In the past, this was done on one screen, but updated MDE has two separate screens now for these actions.
Another change is that you can now toggle and refresh to see if any new FastPass times appear. For example, say the earliest time available for an attraction is 5:20 PM. You can toggle the times by grabbing them and pulling them to the right to refresh making potentially earlier times show up.