I tryed to create a tree in Blender 2.79, but unfortunately i cannot find Sampling: Add tree and Load Preset in the toolbar when I open the file I saved before. Here the screen that appear to me:
It's at the very bottom of the T bar. It might even be hidden, in which case, you would have a little + icon to click on:
Note that this menu is available only right after creating the tree. As soon as you do anything else, the tree can't be changed and the menu will be gone.