When I change a train schedule and then re-save it as the same name line it was already on, the Line definition changes but other trains on the line don't seem to update to the new schedule. Is there some other way to accomplish this?

If i remember correctly the other trains on that line should update their schedule when they arrive at a station or when they leave it.

there is a remote call you can use to display some flying text when a train does certain things, including update it's schedule. /c remote.call("st", "toggleFlyingText")
I'll take a look at your PR over on github today and turn that remote call into a setting or actual command.