You can now add the second step of the model to this page by clicking the area near the with the right mouse button and choose the only option available Add Next Step:
Depending on the renderer you use and the power of your computer the screen will update in a few seconds and look like Screen B.
Note the following:
The number of pages have decreased by one.
Some LPub metacommands were added to the LDraw file structure. These are shown in red and all start with !LPUB.
The assembly of the first and second step are shown in column in the center of the page.
The page layout has changed.