Where is Improved Tracking in the Hunter talent tree?

Survival tree, row 1, column 2. It is available as soon as you have your first talent point at level 10.

Is Improved Tracking new in WoW Forever?

Yes. Improved Tracking has no Classic 1.12 counterpart.

Rank	Effect	Source
1	While tracking Beasts, Demons, Dragonkin, Elementals, Giants, Humanoids, or Undead, all damage you deal to the tracked creature type is increased by 1%.	client
2	While tracking Beasts, Demons, Dragonkin, Elementals, Giants, Humanoids, or Undead, all damage you deal to the tracked creature type is increased by 2%.	client
3	While tracking Beasts, Demons, Dragonkin, Elementals, Giants, Humanoids, or Undead, all damage you deal to the tracked creature type is increased by 3%.	client
4	While tracking Beasts, Demons, Dragonkin, Elementals, Giants, Humanoids, or Undead, all damage you deal to the tracked creature type is increased by 4%.	client
5	While tracking Beasts, Demons, Dragonkin, Elementals, Giants, Humanoids, or Undead, all damage you deal to the tracked creature type is increased by 5%.	client

Tree: Survival, row 1, column 2. Available from your first talent point. The earliest you can finish all 5 ranks is level 14 if you put every point into this tree.
Competes with: Deflection in the same row.

Improved Tracking is new in WoW Forever. Nothing in Classic 1.12 does this for Hunters; it takes the slot of Monster Slaying,Humanoid Slaying.