Several marker lanes would be very useful to organize and discern different sets and type of markers.
A specific marker lane (like the "arrangement track" in Logic) can be used to delimitate song sections (verse, chorus, bridge, etc) and can have specific characteristics: markers in this lane should be contiguous time ranges and their boundaries should be draggable; they should be renamed by double-clicking the range.
Several marker lanes can be used to store different kinds of information - for example, to refer to different playlists.
The user could freely add or remove marker lanes. Marker lanes themselves could be user-renamable to be more descriptive.