Do you mean something like this?
Here's some rough code. It's using a basic control system, not tank individual forward/back on each track, but shows the idea.
It finds where the pivot point is (under a track), rotates the offset to the pivot point and adds the result back to the pivot point to get the final position.
func _process(delta):
var left = Input.is_action_pressed("ui_left")
var right = Input.is_action_pressed("ui_right")
if left && !right:
var pivot = position+Vector2(-40,0).rotated(rotation)
rotation += -2*delta
position = pivot-Vector2(-40,0).rotated(rotation)
if !left && right:
var pivot = position+Vector2(40,0).rotated(rotation)
rotation += 2*delta
position = pivot-Vector2(40,0).rotated(rotation)
if Input.is_action_pressed("ui_up"):
translate(Vector2(0,-200).rotated(rotation)*delta)
if Input.is_action_pressed("ui_down"):
translate(Vector2(0,200).rotated(rotation)*delta)
