"How about a right click on a mouse, that opens a menu that has the following:
Delete selected track
Add New Track (In selecting this it ask above or below existing track, then ask how many tracks)"
That would work too. "+" is common

"Yes but the user should first select the tracks then pull the edge."
Not really. Feature is called track auto zoom. Without selecting particular track, "pulling" any edge, zooms all dynamically. Selecting track will make track zoom independently from the rest.