It seems that the Marker track cannot be renamed. I can click and type in a new name, but upon hitting return it returns to it’s default name (usually “Marker”) without fail. Lately I’ve been getting MIDI files from a client and the Marker track included in these are named “MIDI”, which also cannot be changed. Could there be a more useless name for a track? 
Sometimes I use the Marker track for a very specific purpose for a while and then delete and do something else with it. As such, at any given time it would be quite helpful to know what the markers are actually for, in which case a custom name for the track would be great. How about it Steinberg?