CAD problem: there is one in the model for greening the upper and lower trees. How to create two viewports in the layout, one showing only the upper wood and the other showing only the lower wood?

This is the window freeze function used.

You should first double-click in the viewport area to enter the viewport, then click the layer drop-down table (that is, click the layer name), and then click the third button on the left of the layer you don't want to display to freeze the current viewport, which is a small box with a small sun.

Give it a try and you'll understand!