Q7. The tree is gone. I cannot recall it back, even after pressing F3.

• The tree may be too small to see, like a dot on the screen. This will happen when you activate the tree and zoom it out too much.

• First, activate the tree by clicking the white coordinate system at the lower right-hand corner. (Fig1)

• Then click "Fit all in" icon.(Fig2)

(Fig 1)

(Fig 2)