I have about 2 K miles on my 2010 Prius. I did not notice it immediately but the transmission isn't holding well on hills. The car slips about a foot. Is this normal or expected? Could this be related to a recent incident where the traction control light came on and took turning off the car to reset?
Sounds normal enough to me. With my foot off the gas, it only holds on the slightest of inclines. Anything more than a tiny incline and I have to use the brakes. Your traction light 'issue' may well have been the hill hold assist feature. Plenty of information on the forum and in the owner's manual about the feature.
To activate hill hold, press firmly on the brake pedal at a stop (i.e. far more than you need to hold on the hill). Doing so for 2-3 seconds should activate the hill hold feature. This will hold the brakes for 2 seconds after release which should give you enough time to depress the accelerator to prevent rolling backward. This feature is outlined on page 243 in your owner's manual.
HIll Start Assist is something you should try. It works well. Spend the time to acquaint yourself with this feature is outlined on page 243 in your owner's manual.